mainline inclusion
from mainline-v6.1-rc1
commit 018ee47f
category: feature
bugzilla: https://gitee.com/openeuler/open-source-summer/issues/I55Z0L
CVE: NA
Reference: https://android-review.googlesource.com/c/kernel/common/+/2050912/10

----------------------------------------------------------------------

Searching the rmap for PTEs mapping each page on an LRU list (to test
and clear the accessed bit) can be expensive because pages from
different VMAs (PA space) are not cache friendly to the rmap (VA
space). For workloads mostly using mapped pages, the rmap has a high
CPU cost in the reclaim path.

This patch exploits spatial locality to reduce the trips into the
rmap. When shrink_page_list() walks the rmap and finds a young PTE, a
new function lru_gen_look_around() scans at most BITS_PER_LONG-1
adjacent PTEs. On finding another young PTE, it clears the accessed
bit and updates the gen counter of the page mapped by this PTE to
(max_seq%MAX_NR_GENS)+1.

Server benchmark results:
  Single workload:
    fio (buffered I/O): no change

  Single workload:
    memcached (anon): +[4, 6]%
                         Ops/sec      KB/sec
      patch1-6:          964656.80    37520.88
      patch1-7:          1014393.57   39455.42

  Configurations:
    no change

Client benchmark results:
  kswapd profiles:
    patch1-6
      36.13%  lzo1x_1_do_compress (real work)
      19.16%  page_vma_mapped_walk
       6.55%  _raw_spin_unlock_irq
       4.02%  do_raw_spin_lock
       2.32%  anon_vma_interval_tree_iter_first
       2.11%  ptep_clear_flush
       1.76%  __zram_bvec_write
       1.64%  folio_referenced_one
       1.40%  memmove
       1.35%  obj_malloc

    patch1-7
      45.54%  lzo1x_1_do_compress (real work)
       9.56%  page_vma_mapped_walk
       6.70%  _raw_spin_unlock_irq
       2.78%  ptep_clear_flush
       2.47%  do_raw_spin_lock
       2.22%  __zram_bvec_write
       1.87%  lru_gen_look_around
       1.78%  memmove
       1.77%  obj_malloc
       1.44%  free_unref_page_list

  Configurations:
    no change

Link: https://lore.kernel.org/r/20220309021230.721028-8-yuzhao@google.com/Signed-off-by: NYu Zhao <yuzhao@google.com>
Acked-by: NBrian Geffon <bgeffon@google.com>
Acked-by: NJan Alexander Steffens (heftig) <heftig@archlinux.org>
Acked-by: NOleksandr Natalenko <oleksandr@natalenko.name>
Acked-by: NSteven Barrett <steven@liquorix.net>
Acked-by: NSuleiman Souhlal <suleiman@google.com>
Tested-by: NDaniel Byrne <djbyrne@mtu.edu>
Tested-by: NDonald Carr <d@chaos-reins.com>
Tested-by: NHolger Hoffstätte <holger@applied-asynchrony.com>
Tested-by: NKonstantin Kharlamov <Hi-Angel@yandex.ru>
Tested-by: NShuang Zhai <szhai2@cs.rochester.edu>
Tested-by: NSofia Trinh <sofia.trinh@edi.works>
Tested-by: NVaibhav Jain <vaibhav@linux.ibm.com>
Bug: 227651406
Signed-off-by: NKalesh Singh <kaleshsingh@google.com>
Change-Id: I9a290343840f3cf925c891c8e360c7cdc24ffb9c
Signed-off-by: NYuLinjia <3110442349@qq.com>