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The abd child/parent relationship does not need to be tracked 

ABD's currently track their parent/child relationship.  This applies to
`abd_get_offset()` and `abd_borrow_buf()`.  However, nothing depends on
knowing this relationship, it's only used for consistency checks to
verify that we are not destroying an ABD that's still in use.  When we
are creating/destroying ABD's frequently, the performance impact of
maintaining these data structures (in particular the atomic
increment/decrement operations) can be measurable.

This commit removes this verification code on production builds, but
keeps it when ZFS_DEBUG is set.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Brian Atkinson <batkinson@lanl.gov>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Closes #11535
This commit is contained in:
Matthew Ahrens 2021-01-30 10:04:42 -08:00 committed by GitHub
parent cf0a6dd3ed
commit 2d4bbd14fc
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 19 additions and 1 deletions
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2
include/sys/abd.h
View File

@ -52,8 +52,10 @@ typedef struct abd {
abd_flags_t abd_flags;
uint_t abd_size; /* excludes scattered abd_offset */
list_node_t abd_gang_link;
#ifdef ZFS_DEBUG
struct abd *abd_parent;
zfs_refcount_t abd_children;
#endif
kmutex_t abd_mtx;
union {
struct abd_scatter {

18
module/zfs/abd.c
View File

@ -114,7 +114,9 @@ abd_verify(abd_t *abd)
ABD_FLAG_OWNER | ABD_FLAG_META | ABD_FLAG_MULTI_ZONE |
ABD_FLAG_MULTI_CHUNK | ABD_FLAG_LINEAR_PAGE | ABD_FLAG_GANG |
ABD_FLAG_GANG_FREE | ABD_FLAG_ZEROS | ABD_FLAG_ALLOCD));
#ifdef ZFS_DEBUG
IMPLY(abd->abd_parent != NULL, !(abd->abd_flags & ABD_FLAG_OWNER));
#endif
IMPLY(abd->abd_flags & ABD_FLAG_META, abd->abd_flags & ABD_FLAG_OWNER);
if (abd_is_linear(abd)) {
ASSERT3P(ABD_LINEAR_BUF(abd), !=, NULL);
@ -138,9 +140,11 @@ abd_init_struct(abd_t *abd)
{
list_link_init(&abd->abd_gang_link);
mutex_init(&abd->abd_mtx, NULL, MUTEX_DEFAULT, NULL);
zfs_refcount_create(&abd->abd_children);
abd->abd_flags = 0;
#ifdef ZFS_DEBUG
zfs_refcount_create(&abd->abd_children);
abd->abd_parent = NULL;
#endif
abd->abd_size = 0;
}
@ -149,7 +153,9 @@ abd_fini_struct(abd_t *abd)
{
mutex_destroy(&abd->abd_mtx);
ASSERT(!list_link_active(&abd->abd_gang_link));
#ifdef ZFS_DEBUG
zfs_refcount_destroy(&abd->abd_children);
#endif
}
abd_t *
@ -288,7 +294,9 @@ abd_free(abd_t *abd)
return;
abd_verify(abd);
#ifdef ZFS_DEBUG
IMPLY(abd->abd_flags & ABD_FLAG_OWNER, abd->abd_parent == NULL);
#endif
if (abd_is_gang(abd)) {
abd_free_gang(abd);
@ -300,10 +308,12 @@ abd_free(abd_t *abd)
abd_free_scatter(abd);
}
#ifdef ZFS_DEBUG
if (abd->abd_parent != NULL) {
(void) zfs_refcount_remove_many(&abd->abd_parent->abd_children,
abd->abd_size, abd);
}
#endif
abd_fini_struct(abd);
if (abd->abd_flags & ABD_FLAG_ALLOCD)
@ -526,8 +536,10 @@ abd_get_offset_impl(abd_t *abd, abd_t *sabd, size_t off, size_t size)
ASSERT3P(abd, !=, NULL);
abd->abd_size = size;
#ifdef ZFS_DEBUG
abd->abd_parent = sabd;
(void) zfs_refcount_add_many(&sabd->abd_children, abd->abd_size, abd);
#endif
return (abd);
}
@ -624,7 +636,9 @@ abd_borrow_buf(abd_t *abd, size_t n)
} else {
buf = zio_buf_alloc(n);
}
#ifdef ZFS_DEBUG
(void) zfs_refcount_add_many(&abd->abd_children, n, buf);
#endif
return (buf);
}
@ -655,7 +669,9 @@ abd_return_buf(abd_t *abd, void *buf, size_t n)
ASSERT0(abd_cmp_buf(abd, buf, n));
zio_buf_free(buf, n);
}
#ifdef ZFS_DEBUG
(void) zfs_refcount_remove_many(&abd->abd_children, n, buf);
#endif
}
void