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The ->percpu_pvec_drained was originally introduced by commitd9ed0d08b6("mm: only drain per-cpu pagevecs once per pagevec usage") to drain per-cpu pagevecs only once per pagevec usage. But after converting the swap code to be more folio-based, the commitc2bc16817a("mm/swap: add folio_batch_move_lru()") breaks this logic, which would cause ->percpu_pvec_drained to be reset to false, that means per-cpu pagevecs will be drained multiple times per pagevec usage. In theory, there should be no functional changes when converting code to be more folio-based. We should call folio_batch_reinit() in folio_batch_move_lru() instead of folio_batch_init(). And to verify that we still need ->percpu_pvec_drained, I ran mmtests/sparsetruncate-tiny and got the following data: baseline with baseline/ patch/ Min Time 326.00 ( 0.00%) 328.00 ( -0.61%) 1st-qrtle Time 334.00 ( 0.00%) 336.00 ( -0.60%) 2nd-qrtle Time 338.00 ( 0.00%) 341.00 ( -0.89%) 3rd-qrtle Time 343.00 ( 0.00%) 347.00 ( -1.17%) Max-1 Time 326.00 ( 0.00%) 328.00 ( -0.61%) Max-5 Time 327.00 ( 0.00%) 330.00 ( -0.92%) Max-10 Time 328.00 ( 0.00%) 331.00 ( -0.91%) Max-90 Time 350.00 ( 0.00%) 357.00 ( -2.00%) Max-95 Time 395.00 ( 0.00%) 390.00 ( 1.27%) Max-99 Time 508.00 ( 0.00%) 434.00 ( 14.57%) Max Time 547.00 ( 0.00%) 476.00 ( 12.98%) Amean Time 344.61 ( 0.00%) 345.56 * -0.28%* Stddev Time 30.34 ( 0.00%) 19.51 ( 35.69%) CoeffVar Time 8.81 ( 0.00%) 5.65 ( 35.87%) BAmean-99 Time 342.38 ( 0.00%) 344.27 ( -0.55%) BAmean-95 Time 338.58 ( 0.00%) 341.87 ( -0.97%) BAmean-90 Time 336.89 ( 0.00%) 340.26 ( -1.00%) BAmean-75 Time 335.18 ( 0.00%) 338.40 ( -0.96%) BAmean-50 Time 332.54 ( 0.00%) 335.42 ( -0.87%) BAmean-25 Time 329.30 ( 0.00%) 332.00 ( -0.82%) From the above it can be seen that we get similar data to when ->percpu_pvec_drained was introduced, so we still need it. Let's call folio_batch_reinit() in folio_batch_move_lru() to restore the original logic. Link: https://lkml.kernel.org/r/20230405161854.6931-1-zhengqi.arch@bytedance.com Fixes:c2bc16817a("mm/swap: add folio_batch_move_lru()") Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> Acked-by: Mel Gorman <mgorman@suse.de> Cc: Lorenzo Stoakes <lstoakes@gmail.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.