libzpool/abd_os: iovec-based scatter abd
This is intended to be a simple userspace scatter abd based on struct iovec. It's not very sophisticated as-is, but sets a base for something much more interesting. Sponsored-by: Klara, Inc. Sponsored-by: Wasabi Technology, Inc. Reviewed-by: Alexander Motin <mav@FreeBSD.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Rob Norris <rob.norris@klarasystems.com> Closes #16253
This commit is contained in:
Rob Norris
Brian Behlendorf
parent
5b9e695392
commit
b69bebb535
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@ -24,34 +24,6 @@
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* Copyright (c) 2023, 2024, Klara Inc.
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*/
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/*
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* See abd.c for a general overview of the arc buffered data (ABD).
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*
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* Linear buffers act exactly like normal buffers and are always mapped into the
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* kernel's virtual memory space, while scattered ABD data chunks are allocated
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* as physical pages and then mapped in only while they are actually being
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* accessed through one of the abd_* library functions. Using scattered ABDs
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* provides several benefits:
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*
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* (1) They avoid use of kmem_*, preventing performance problems where running
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* kmem_reap on very large memory systems never finishes and causes
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* constant TLB shootdowns.
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*
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* (2) Fragmentation is less of an issue since when we are at the limit of
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* allocatable space, we won't have to search around for a long free
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* hole in the VA space for large ARC allocations. Each chunk is mapped in
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* individually, so even if we are using HIGHMEM (see next point) we
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* wouldn't need to worry about finding a contiguous address range.
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*
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* (3) If we are not using HIGHMEM, then all physical memory is always
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* mapped into the kernel's address space, so we also avoid the map /
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* unmap costs on each ABD access.
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*
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* If we are not using HIGHMEM, scattered buffers which have only one chunk
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* can be treated as linear buffers, because they are contiguous in the
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* kernel's virtual address space. See abd_alloc_chunks() for details.
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*/
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#include <sys/abd_impl.h>
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#include <sys/param.h>
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#include <sys/zio.h>
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@ -59,199 +31,112 @@
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#include <sys/zfs_context.h>
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#include <sys/zfs_znode.h>
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#define abd_for_each_sg(abd, sg, n, i) \
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for_each_sg(ABD_SCATTER(abd).abd_sgl, sg, n, i)
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/*
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* We're simulating scatter/gather with 4K allocations, since that's more like
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* what a typical kernel does.
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*/
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#define ABD_PAGESIZE (4096)
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#define ABD_PAGESHIFT (12)
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#define ABD_PAGEMASK (ABD_PAGESIZE-1)
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/*
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* zfs_abd_scatter_min_size is the minimum allocation size to use scatter
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* ABD's. Smaller allocations will use linear ABD's which uses
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* zio_[data_]buf_alloc().
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*
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* Scatter ABD's use at least one page each, so sub-page allocations waste
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* some space when allocated as scatter (e.g. 2KB scatter allocation wastes
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* half of each page). Using linear ABD's for small allocations means that
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* they will be put on slabs which contain many allocations. This can
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* improve memory efficiency, but it also makes it much harder for ARC
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* evictions to actually free pages, because all the buffers on one slab need
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* to be freed in order for the slab (and underlying pages) to be freed.
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* Typically, 512B and 1KB kmem caches have 16 buffers per slab, so it's
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* possible for them to actually waste more memory than scatter (one page per
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* buf = wasting 3/4 or 7/8th; one buf per slab = wasting 15/16th).
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*
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* Spill blocks are typically 512B and are heavily used on systems running
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* selinux with the default dnode size and the `xattr=sa` property set.
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*
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* By default we use linear allocations for 512B and 1KB, and scatter
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* allocations for larger (1.5KB and up).
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* See rationale in module/os/linux/zfs/abd_os.c, but in userspace this is
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* mostly useful to get a mix of linear and scatter ABDs for testing.
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*/
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static int zfs_abd_scatter_min_size = 512 * 3;
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#define ABD_SCATTER_MIN_SIZE (512 * 3)
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/*
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* We use a scattered SPA_MAXBLOCKSIZE sized ABD whose pages are
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* just a single zero'd page. This allows us to conserve memory by
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* only using a single zero page for the scatterlist.
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*/
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abd_t *abd_zero_scatter = NULL;
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struct page;
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/*
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* abd_zero_page will be allocated with a zero'ed PAGESIZE buffer, which is
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* assigned to each of the pages of abd_zero_scatter.
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*/
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static struct page *abd_zero_page = NULL;
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static kmem_cache_t *abd_cache = NULL;
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static uint_t
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abd_chunkcnt_for_bytes(size_t size)
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abd_iovcnt_for_bytes(size_t size)
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{
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return (P2ROUNDUP(size, PAGESIZE) / PAGESIZE);
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/*
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* Each iovec points to a 4K page. There's no real reason to do this
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* in userspace, but our whole point here is to make it feel a bit
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* more like a real paged memory model.
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*/
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return (P2ROUNDUP(size, ABD_PAGESIZE) / ABD_PAGESIZE);
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}
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abd_t *
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abd_alloc_struct_impl(size_t size)
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{
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/*
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* In Linux we do not use the size passed in during ABD
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* allocation, so we just ignore it.
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* Zero-sized means it will be used for a linear or gang abd, so just
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* allocate the abd itself and return.
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*/
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(void) size;
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abd_t *abd = kmem_cache_alloc(abd_cache, KM_PUSHPAGE);
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ASSERT3P(abd, !=, NULL);
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if (size == 0)
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return (umem_alloc(sizeof (abd_t), UMEM_NOFAIL));
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/*
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* Allocating for a scatter abd, so compute how many ABD_PAGESIZE
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* iovecs we will need to hold this size. Append that allocation to the
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* end. Note that struct abd_scatter has includes abd_iov[1], so we
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* allocate one less iovec than we need.
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*
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* Note we're not allocating the pages proper, just the iovec pointers.
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* That's down in abd_alloc_chunks. We _could_ do it here in a single
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* allocation, but it's fiddly and harder to read for no real gain.
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*/
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uint_t n = abd_iovcnt_for_bytes(size);
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abd_t *abd = umem_alloc(sizeof (abd_t) + (n-1) * sizeof (struct iovec),
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UMEM_NOFAIL);
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ABD_SCATTER(abd).abd_offset = 0;
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ABD_SCATTER(abd).abd_iovcnt = n;
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return (abd);
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}
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void
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abd_free_struct_impl(abd_t *abd)
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{
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kmem_cache_free(abd_cache, abd);
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}
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#define nth_page(pg, i) \
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((struct page *)((void *)(pg) + (i) * PAGESIZE))
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struct scatterlist {
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struct page *page;
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int length;
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int end;
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};
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static void
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sg_init_table(struct scatterlist *sg, int nr)
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{
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memset(sg, 0, nr * sizeof (struct scatterlist));
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sg[nr - 1].end = 1;
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}
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/*
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* This must be called if any of the sg_table allocation functions
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* are called.
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*/
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static void
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abd_free_sg_table(abd_t *abd)
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{
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int nents = ABD_SCATTER(abd).abd_nents;
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vmem_free(ABD_SCATTER(abd).abd_sgl,
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nents * sizeof (struct scatterlist));
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}
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#define for_each_sg(sgl, sg, nr, i) \
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for ((i) = 0, (sg) = (sgl); (i) < (nr); (i)++, (sg) = sg_next(sg))
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static inline void
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sg_set_page(struct scatterlist *sg, struct page *page, unsigned int len,
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unsigned int offset)
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{
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/* currently we don't use offset */
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ASSERT(offset == 0);
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sg->page = page;
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sg->length = len;
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}
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static inline struct page *
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sg_page(struct scatterlist *sg)
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{
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return (sg->page);
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}
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static inline struct scatterlist *
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sg_next(struct scatterlist *sg)
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{
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if (sg->end)
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return (NULL);
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return (sg + 1);
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/* For scatter, compute the extra amount we need to free */
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uint_t iovcnt =
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abd_is_linear(abd) || abd_is_gang(abd) ?
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0 : (ABD_SCATTER(abd).abd_iovcnt - 1);
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umem_free(abd, sizeof (abd_t) + iovcnt * sizeof (struct iovec));
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}
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void
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abd_alloc_chunks(abd_t *abd, size_t size)
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{
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unsigned nr_pages = abd_chunkcnt_for_bytes(size);
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struct scatterlist *sg;
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int i;
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/*
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* We've already allocated the iovec array; ensure that the wanted size
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* actually matches, otherwise the caller has made a mistake somewhere.
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*/
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uint_t n = ABD_SCATTER(abd).abd_iovcnt;
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ASSERT3U(n, ==, abd_iovcnt_for_bytes(size));
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ABD_SCATTER(abd).abd_sgl = vmem_alloc(nr_pages *
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sizeof (struct scatterlist), KM_SLEEP);
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sg_init_table(ABD_SCATTER(abd).abd_sgl, nr_pages);
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abd_for_each_sg(abd, sg, nr_pages, i) {
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struct page *p = umem_alloc_aligned(PAGESIZE, 64, KM_SLEEP);
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sg_set_page(sg, p, PAGESIZE, 0);
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/*
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* Allocate a ABD_PAGESIZE region for each iovec.
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*/
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struct iovec *iov = ABD_SCATTER(abd).abd_iov;
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for (int i = 0; i < n; i++) {
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iov[i].iov_base =
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umem_alloc_aligned(ABD_PAGESIZE, ABD_PAGESIZE, UMEM_NOFAIL);
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iov[i].iov_len = ABD_PAGESIZE;
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}
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ABD_SCATTER(abd).abd_nents = nr_pages;
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}
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void
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abd_free_chunks(abd_t *abd)
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{
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int i, n = ABD_SCATTER(abd).abd_nents;
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struct scatterlist *sg;
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abd_for_each_sg(abd, sg, n, i) {
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struct page *p = nth_page(sg_page(sg), 0);
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umem_free_aligned(p, PAGESIZE);
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}
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abd_free_sg_table(abd);
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}
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static void
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abd_alloc_zero_scatter(void)
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{
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unsigned nr_pages = abd_chunkcnt_for_bytes(SPA_MAXBLOCKSIZE);
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struct scatterlist *sg;
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int i;
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abd_zero_page = umem_alloc_aligned(PAGESIZE, 64, KM_SLEEP);
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memset(abd_zero_page, 0, PAGESIZE);
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abd_zero_scatter = abd_alloc_struct(SPA_MAXBLOCKSIZE);
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abd_zero_scatter->abd_flags |= ABD_FLAG_OWNER;
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abd_zero_scatter->abd_flags |= ABD_FLAG_MULTI_CHUNK;
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ABD_SCATTER(abd_zero_scatter).abd_offset = 0;
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ABD_SCATTER(abd_zero_scatter).abd_nents = nr_pages;
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abd_zero_scatter->abd_size = SPA_MAXBLOCKSIZE;
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ABD_SCATTER(abd_zero_scatter).abd_sgl = vmem_alloc(nr_pages *
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sizeof (struct scatterlist), KM_SLEEP);
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sg_init_table(ABD_SCATTER(abd_zero_scatter).abd_sgl, nr_pages);
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abd_for_each_sg(abd_zero_scatter, sg, nr_pages, i) {
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sg_set_page(sg, abd_zero_page, PAGESIZE, 0);
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}
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uint_t n = ABD_SCATTER(abd).abd_iovcnt;
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struct iovec *iov = ABD_SCATTER(abd).abd_iov;
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for (int i = 0; i < n; i++)
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umem_free_aligned(iov[i].iov_base, ABD_PAGESIZE);
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}
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boolean_t
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abd_size_alloc_linear(size_t size)
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{
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return (!zfs_abd_scatter_enabled || size < zfs_abd_scatter_min_size);
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return (size < ABD_SCATTER_MIN_SIZE);
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}
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void
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abd_update_scatter_stats(abd_t *abd, abd_stats_op_t op)
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{
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ASSERT(op == ABDSTAT_INCR || op == ABDSTAT_DECR);
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int waste = P2ROUNDUP(abd->abd_size, PAGESIZE) - abd->abd_size;
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int waste = P2ROUNDUP(abd->abd_size, ABD_PAGESIZE) - abd->abd_size;
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if (op == ABDSTAT_INCR) {
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arc_space_consume(waste, ARC_SPACE_ABD_CHUNK_WASTE);
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} else {
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@ -270,67 +155,72 @@ abd_update_linear_stats(abd_t *abd, abd_stats_op_t op)
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void
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abd_verify_scatter(abd_t *abd)
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{
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size_t n;
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int i = 0;
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struct scatterlist *sg = NULL;
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#ifdef ZFS_DEBUG
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/*
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* scatter abds shall have:
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* - at least one iovec
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* - all iov_base point somewhere
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* - all iov_len are ABD_PAGESIZE
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* - offset set within the abd pages somewhere
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*/
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uint_t n = ABD_SCATTER(abd).abd_iovcnt;
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ASSERT3U(n, >, 0);
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ASSERT3U(ABD_SCATTER(abd).abd_nents, >, 0);
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ASSERT3U(ABD_SCATTER(abd).abd_offset, <,
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ABD_SCATTER(abd).abd_sgl->length);
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n = ABD_SCATTER(abd).abd_nents;
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abd_for_each_sg(abd, sg, n, i) {
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ASSERT3P(sg_page(sg), !=, NULL);
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uint_t len = 0;
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for (int i = 0; i < n; i++) {
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ASSERT3P(ABD_SCATTER(abd).abd_iov[i].iov_base, !=, NULL);
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ASSERT3U(ABD_SCATTER(abd).abd_iov[i].iov_len, ==, ABD_PAGESIZE);
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len += ABD_PAGESIZE;
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}
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}
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static void
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abd_free_zero_scatter(void)
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{
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abd_free_sg_table(abd_zero_scatter);
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abd_free_struct(abd_zero_scatter);
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abd_zero_scatter = NULL;
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ASSERT3P(abd_zero_page, !=, NULL);
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umem_free_aligned(abd_zero_page, PAGESIZE);
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ASSERT3U(ABD_SCATTER(abd).abd_offset, <, len);
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#endif
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}
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void
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abd_init(void)
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{
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abd_cache = kmem_cache_create("abd_t", sizeof (abd_t),
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0, NULL, NULL, NULL, NULL, NULL, 0);
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/*
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* Create the "zero" scatter abd. This is always the size of the
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* largest possible block, but only actually has a single allocated
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* page, which all iovecs in the abd point to.
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*/
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abd_zero_scatter = abd_alloc_struct(SPA_MAXBLOCKSIZE);
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abd_zero_scatter->abd_flags |= ABD_FLAG_OWNER;
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abd_zero_scatter->abd_size = SPA_MAXBLOCKSIZE;
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abd_alloc_zero_scatter();
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void *zero =
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umem_alloc_aligned(ABD_PAGESIZE, ABD_PAGESIZE, UMEM_NOFAIL);
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memset(zero, 0, ABD_PAGESIZE);
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uint_t n = abd_iovcnt_for_bytes(SPA_MAXBLOCKSIZE);
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struct iovec *iov = ABD_SCATTER(abd_zero_scatter).abd_iov;
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for (int i = 0; i < n; i++) {
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iov[i].iov_base = zero;
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iov[i].iov_len = ABD_PAGESIZE;
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}
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}
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void
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abd_fini(void)
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{
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abd_free_zero_scatter();
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if (abd_cache) {
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kmem_cache_destroy(abd_cache);
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abd_cache = NULL;
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}
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umem_free_aligned(
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ABD_SCATTER(abd_zero_scatter).abd_iov[0].iov_base, ABD_PAGESIZE);
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abd_free_struct(abd_zero_scatter);
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abd_zero_scatter = NULL;
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}
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void
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abd_free_linear_page(abd_t *abd)
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{
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/*
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* LINEAR_PAGE is specific to the Linux kernel; we never set this
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* flag, so this will never be called.
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*/
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(void) abd;
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__builtin_unreachable();
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PANIC("unreachable");
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}
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/*
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* If we're going to use this ABD for doing I/O using the block layer, the
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* consumer of the ABD data doesn't care if it's scattered or not, and we don't
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* plan to store this ABD in memory for a long period of time, we should
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* allocate the ABD type that requires the least data copying to do the I/O.
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*
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* On Linux the optimal thing to do would be to use abd_get_offset() and
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* construct a new ABD which shares the original pages thereby eliminating
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* the copy. But for the moment a new linear ABD is allocated until this
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* performance optimization can be implemented.
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*/
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abd_t *
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abd_alloc_for_io(size_t size, boolean_t is_metadata)
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{
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@ -338,43 +228,60 @@ abd_alloc_for_io(size_t size, boolean_t is_metadata)
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}
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abd_t *
|
||||
abd_get_offset_scatter(abd_t *abd, abd_t *sabd, size_t off,
|
||||
size_t size)
|
||||
abd_get_offset_scatter(abd_t *dabd, abd_t *sabd, size_t off, size_t size)
|
||||
{
|
||||
(void) size;
|
||||
int i = 0;
|
||||
struct scatterlist *sg = NULL;
|
||||
|
||||
abd_verify(sabd);
|
||||
ASSERT3U(off, <=, sabd->abd_size);
|
||||
|
||||
size_t new_offset = ABD_SCATTER(sabd).abd_offset + off;
|
||||
|
||||
if (abd == NULL)
|
||||
abd = abd_alloc_struct(0);
|
||||
|
||||
/*
|
||||
* Even if this buf is filesystem metadata, we only track that
|
||||
* if we own the underlying data buffer, which is not true in
|
||||
* this case. Therefore, we don't ever use ABD_FLAG_META here.
|
||||
* Create a new scatter dabd by borrowing data pages from sabd to cover
|
||||
* off+size.
|
||||
*
|
||||
* sabd is an existing scatter abd with a set of iovecs, each covering
|
||||
* an ABD_PAGESIZE (4K) allocation. It's "zero" is at abd_offset.
|
||||
*
|
||||
* [........][........][........][........]
|
||||
* ^- sabd_offset
|
||||
*
|
||||
* We want to produce a new abd, referencing those allocations at the
|
||||
* given offset.
|
||||
*
|
||||
* [........][........][........][........]
|
||||
* ^- dabd_offset = sabd_offset + off
|
||||
* ^- dabd_offset + size
|
||||
*
|
||||
* In this example, dabd needs three iovecs. The first iovec is offset
|
||||
* 0, so the final dabd_offset is masked back into the first iovec.
|
||||
*
|
||||
* [........][........][........]
|
||||
* ^- dabd_offset
|
||||
*/
|
||||
size_t soff = ABD_SCATTER(sabd).abd_offset + off;
|
||||
size_t doff = soff & ABD_PAGEMASK;
|
||||
size_t iovcnt = abd_iovcnt_for_bytes(doff + size);
|
||||
|
||||
abd_for_each_sg(sabd, sg, ABD_SCATTER(sabd).abd_nents, i) {
|
||||
if (new_offset < sg->length)
|
||||
break;
|
||||
new_offset -= sg->length;
|
||||
}
|
||||
/*
|
||||
* If the passed-in abd has enough allocated iovecs already, reuse it.
|
||||
* Otherwise, make a new one. The caller will free the original if the
|
||||
* one it gets back is not the same.
|
||||
*
|
||||
* Note that it's ok if we reuse an abd with more iovecs than we need.
|
||||
* abd_size has the usable amount of data, and the abd does not own the
|
||||
* pages referenced by the iovecs. At worst, they're holding dangling
|
||||
* pointers that we'll never use anyway.
|
||||
*/
|
||||
if (dabd == NULL || ABD_SCATTER(dabd).abd_iovcnt < iovcnt)
|
||||
dabd = abd_alloc_struct(iovcnt << ABD_PAGESHIFT);
|
||||
|
||||
ABD_SCATTER(abd).abd_sgl = sg;
|
||||
ABD_SCATTER(abd).abd_offset = new_offset;
|
||||
ABD_SCATTER(abd).abd_nents = ABD_SCATTER(sabd).abd_nents - i;
|
||||
/* Set offset into first page in view */
|
||||
ABD_SCATTER(dabd).abd_offset = doff;
|
||||
|
||||
return (abd);
|
||||
/* Copy the wanted iovecs from the source to the dest */
|
||||
memcpy(&ABD_SCATTER(dabd).abd_iov[0],
|
||||
&ABD_SCATTER(sabd).abd_iov[soff >> ABD_PAGESHIFT],
|
||||
iovcnt * sizeof (struct iovec));
|
||||
|
||||
return (dabd);
|
||||
}
|
||||
|
||||
/*
|
||||
* Initialize the abd_iter.
|
||||
*/
|
||||
void
|
||||
abd_iter_init(struct abd_iter *aiter, abd_t *abd)
|
||||
{
|
||||
|
|
@ -382,16 +289,8 @@ abd_iter_init(struct abd_iter *aiter, abd_t *abd)
|
|||
abd_verify(abd);
|
||||
memset(aiter, 0, sizeof (struct abd_iter));
|
||||
aiter->iter_abd = abd;
|
||||
if (!abd_is_linear(abd)) {
|
||||
aiter->iter_offset = ABD_SCATTER(abd).abd_offset;
|
||||
aiter->iter_sg = ABD_SCATTER(abd).abd_sgl;
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* This is just a helper function to see if we have exhausted the
|
||||
* abd_iter and reached the end.
|
||||
*/
|
||||
boolean_t
|
||||
abd_iter_at_end(struct abd_iter *aiter)
|
||||
{
|
||||
|
|
@ -399,83 +298,57 @@ abd_iter_at_end(struct abd_iter *aiter)
|
|||
return (aiter->iter_pos == aiter->iter_abd->abd_size);
|
||||
}
|
||||
|
||||
/*
|
||||
* Advance the iterator by a certain amount. Cannot be called when a chunk is
|
||||
* in use. This can be safely called when the aiter has already exhausted, in
|
||||
* which case this does nothing.
|
||||
*/
|
||||
void
|
||||
abd_iter_advance(struct abd_iter *aiter, size_t amount)
|
||||
{
|
||||
/*
|
||||
* Ensure that last chunk is not in use. abd_iterate_*() must clear
|
||||
* this state (directly or abd_iter_unmap()) before advancing.
|
||||
*/
|
||||
ASSERT3P(aiter->iter_mapaddr, ==, NULL);
|
||||
ASSERT0(aiter->iter_mapsize);
|
||||
ASSERT3P(aiter->iter_page, ==, NULL);
|
||||
ASSERT0(aiter->iter_page_doff);
|
||||
ASSERT0(aiter->iter_page_dsize);
|
||||
|
||||
/* There's nothing left to advance to, so do nothing */
|
||||
if (abd_iter_at_end(aiter))
|
||||
return;
|
||||
|
||||
aiter->iter_pos += amount;
|
||||
aiter->iter_offset += amount;
|
||||
if (!abd_is_linear(aiter->iter_abd)) {
|
||||
while (aiter->iter_offset >= aiter->iter_sg->length) {
|
||||
aiter->iter_offset -= aiter->iter_sg->length;
|
||||
aiter->iter_sg = sg_next(aiter->iter_sg);
|
||||
if (aiter->iter_sg == NULL) {
|
||||
ASSERT0(aiter->iter_offset);
|
||||
break;
|
||||
}
|
||||
}
|
||||
}
|
||||
ASSERT3U(aiter->iter_pos, <=, aiter->iter_abd->abd_size);
|
||||
}
|
||||
|
||||
/*
|
||||
* Map the current chunk into aiter. This can be safely called when the aiter
|
||||
* has already exhausted, in which case this does nothing.
|
||||
*/
|
||||
void
|
||||
abd_iter_map(struct abd_iter *aiter)
|
||||
{
|
||||
void *paddr;
|
||||
size_t offset = 0;
|
||||
|
||||
ASSERT3P(aiter->iter_mapaddr, ==, NULL);
|
||||
ASSERT0(aiter->iter_mapsize);
|
||||
|
||||
/* There's nothing left to iterate over, so do nothing */
|
||||
if (abd_iter_at_end(aiter))
|
||||
return;
|
||||
|
||||
if (abd_is_linear(aiter->iter_abd)) {
|
||||
ASSERT3U(aiter->iter_pos, ==, aiter->iter_offset);
|
||||
offset = aiter->iter_offset;
|
||||
aiter->iter_mapsize = aiter->iter_abd->abd_size - offset;
|
||||
paddr = ABD_LINEAR_BUF(aiter->iter_abd);
|
||||
} else {
|
||||
offset = aiter->iter_offset;
|
||||
aiter->iter_mapsize = MIN(aiter->iter_sg->length - offset,
|
||||
aiter->iter_abd->abd_size - aiter->iter_pos);
|
||||
|
||||
paddr = sg_page(aiter->iter_sg);
|
||||
aiter->iter_mapaddr =
|
||||
ABD_LINEAR_BUF(aiter->iter_abd) + aiter->iter_pos;
|
||||
aiter->iter_mapsize =
|
||||
aiter->iter_abd->abd_size - aiter->iter_pos;
|
||||
return;
|
||||
}
|
||||
|
||||
aiter->iter_mapaddr = (char *)paddr + offset;
|
||||
/*
|
||||
* For scatter, we index into the appropriate iovec, and return the
|
||||
* smaller of the amount requested, or up to the end of the page.
|
||||
*/
|
||||
size_t poff = aiter->iter_pos + ABD_SCATTER(aiter->iter_abd).abd_offset;
|
||||
|
||||
ASSERT3U(poff >> ABD_PAGESHIFT, <=,
|
||||
ABD_SCATTER(aiter->iter_abd).abd_iovcnt);
|
||||
struct iovec *iov = &ABD_SCATTER(aiter->iter_abd).
|
||||
abd_iov[poff >> ABD_PAGESHIFT];
|
||||
|
||||
aiter->iter_mapsize = MIN(ABD_PAGESIZE - (poff & ABD_PAGEMASK),
|
||||
aiter->iter_abd->abd_size - aiter->iter_pos);
|
||||
ASSERT3U(aiter->iter_mapsize, <=, ABD_PAGESIZE);
|
||||
|
||||
aiter->iter_mapaddr = iov->iov_base + (poff & ABD_PAGEMASK);
|
||||
}
|
||||
|
||||
/*
|
||||
* Unmap the current chunk from aiter. This can be safely called when the aiter
|
||||
* has already exhausted, in which case this does nothing.
|
||||
*/
|
||||
void
|
||||
abd_iter_unmap(struct abd_iter *aiter)
|
||||
{
|
||||
/* There's nothing left to unmap, so do nothing */
|
||||
if (abd_iter_at_end(aiter))
|
||||
return;
|
||||
|
||||
|
|
|
|||
|
|
@ -32,8 +32,8 @@ extern "C" {
|
|||
|
||||
struct abd_scatter {
|
||||
uint_t abd_offset;
|
||||
uint_t abd_nents;
|
||||
struct scatterlist *abd_sgl;
|
||||
uint_t abd_iovcnt;
|
||||
struct iovec abd_iov[1]; /* actually variable-length */
|
||||
};
|
||||
|
||||
struct abd_linear {
|
||||
|
|
|
|||
Loading…
Reference in New Issue