3018bffa9b
This change is designed to improve the memory utilization of slabs by more carefully setting their size. The way the code currently works is problematic for slabs which contain large objects (>1MB). This is due to slabs being unconditionally rounded up to a power of two which may result in unused space at the end of the slab. The reason the existing code rounds up every slab is because it assumes it will backed by the buddy allocator. Since the buddy allocator can only performs power of two allocations this is desirable because it avoids wasting any space. However, this logic breaks down if slab is backed by vmalloc() which operates at a page level granularity. In this case, the optimal thing to do is calculate the minimum required slab size given certain constraints (object size, alignment, objects/slab, etc). Therefore, this patch reworks the spl_slab_size() function so that it sizes KMC_KMEM slabs differently than KMC_VMEM slabs. KMC_KMEM slabs are rounded up to the nearest power of two, and KMC_VMEM slabs are allowed to be the minimum required size. This change also reduces the default number of objects per slab. This reduces how much memory a single cache object can pin, which can result in significant memory saving for highly fragmented caches. But depending on the workload it may result in slabs being allocated and freed more frequently. In practice, this has been shown to be a better default for most workloads. Also the maximum slab size has been reduced to 4MB on 32-bit systems. Due to the limited virtual address space it's critical the we be as frugal as possible. A limit of 4M still lets us reasonably comfortably allocate a limited number of 1MB objects. Finally, the kmem:slab_small and kmem:slab_large SPLAT tests were extended to provide better test coverage of various object sizes and alignments. Caches are created with random parameters and their basic functionality is verified by allocating several slabs worth of objects. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> |
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| DISCLAIMER | ||
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| README.markdown | ||
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| copy-builtin | ||
| spl.release.in | ||
README.markdown
The Solaris Porting Layer (SPL) is a Linux kernel module which provides many of the Solaris kernel APIs. This shim layer makes it possible to run Solaris kernel code in the Linux kernel with relatively minimal modification. This can be particularly useful when you want to track upstream Solaris development closely and do not want the overhead of maintaining a large patch which converts Solaris primitives to Linux primitives.
To build packages for your distribution:
$ ./configure
$ make pkg
If you are building directly from the git tree and not an officially released tarball you will need to generate the configure script. This can be done by executing the autogen.sh script after installing the GNU autotools for your distribution.
To copy the kernel code inside your kernel source tree for builtin compilation:
$ ./configure --enable-linux-builtin --with-linux=/usr/src/linux-...
$ ./copy-builtin /usr/src/linux-...
The SPL comes with an automated test suite called SPLAT. The test suite is implemented in two parts. There is a kernel module which contains the tests and a user space utility which controls which tests are run. To run the full test suite:
$ sudo insmod ./module/splat/splat.ko
$ sudo ./cmd/splat --all
Full documentation for building, configuring, testing, and using the SPL can be found at: http://zfsonlinux.org