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A mirror of the official Linux kernel repository just in case
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It's been noted that z3fold doesn't scale well when it's run in a large number of threads on many cores, which can be easily reproduced with fio 'randrw' test with --numjobs=32. E.g. the result for 1 cluster (4 cores) is: Run status group 0 (all jobs): READ: io=244785MB, aggrb=496883KB/s, minb=15527KB/s, ... WRITE: io=246735MB, aggrb=500841KB/s, minb=15651KB/s, ... While for 8 cores (2 clusters) the result is: Run status group 0 (all jobs): READ: io=244785MB, aggrb=265942KB/s, minb=8310KB/s, ... WRITE: io=246735MB, aggrb=268060KB/s, minb=8376KB/s, ... The bottleneck here is the pool lock which many threads become waiting upon. To reduce that spin lock contention, z3fold can operate only on the lists local to the current CPU whenever possible. Due to the nature of z3fold unbuddied list handling (it only takes the first entry off the list on a hot path), if the z3fold pool is big enough and balanced well enough, limiting search to only local unbuddied list doesn't lead to a significant compression ratio degrade (2.57x vs 2.65x in our measurements). This patch also introduces two worker threads: one for async in-page object layout optimization and one for releasing freed pages. This is done to speed up z3fold_free() which is often on a hot path. The fio results for 8-core case are now the following: Run status group 0 (all jobs): READ: io=244785MB, aggrb=1568.3MB/s, minb=50182KB/s, ... WRITE: io=246735MB, aggrb=1580.8MB/s, minb=50582KB/s, ... So we're in for almost 6x performance increase. Link: http://lkml.kernel.org/r/20170806181443.f9b65018f8bde25ef990f9e8@gmail.com Signed-off-by: Vitaly Wool <vitalywool@gmail.com> Cc: Dan Streetman <ddstreet@ieee.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.