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From: Ryan Roberts <ryan.roberts@arm.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	David Hildenbrand <david@redhat.com>,
	Matthew Wilcox <willy@infradead.org>,
	Huang Ying <ying.huang@intel.com>, Gao Xiang <xiang@kernel.org>,
	Yu Zhao <yuzhao@google.com>, Yang Shi <shy828301@gmail.com>,
	Michal Hocko <mhocko@suse.com>,
	Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH v3 0/4] Swap-out small-sized THP without splitting
Date: Wed, 25 Oct 2023 15:45:42 +0100	[thread overview]
Message-ID: <20231025144546.577640-1-ryan.roberts@arm.com> (raw)

Hi All,

This is v3 of a series to add support for swapping out small-sized THP without
needing to first split the large folio via __split_huge_page(). It closely
follows the approach already used by PMD-sized THP.

"Small-sized THP" is an upcoming feature that enables performance improvements
by allocating large folios for anonymous memory, where the large folio size is
smaller than the traditional PMD-size. See [3].

In some circumstances I've observed a performance regression (see patch 2 for
details), and this series is an attempt to fix the regression in advance of
merging small-sized THP support.

I've done what I thought was the smallest change possible, and as a result, this
approach is only employed when the swap is backed by a non-rotating block device
(just as PMD-sized THP is supported today). Discussion against the RFC concluded
that this is probably sufficient.

The series applies against mm-unstable (1a3c85fa684a)


Changes since v2 [2]
====================

 - Reuse scan_swap_map_try_ssd_cluster() between order-0 and order > 0
   allocation. This required some refactoring to make everything work nicely
   (new patches 2 and 3).
 - Fix bug where nr_swap_pages would say there are pages available but the
   scanner would not be able to allocate them because they were reserved for the
   per-cpu allocator. We now allow stealing of order-0 entries from the high
   order per-cpu clusters (in addition to exisiting stealing from order-0
   per-cpu clusters).

Thanks to Huang, Ying for the review feedback and suggestions!


Changes since v1 [1]
====================

 - patch 1:
    - Use cluster_set_count() instead of cluster_set_count_flag() in
      swap_alloc_cluster() since we no longer have any flag to set. I was unable
      to kill cluster_set_count_flag() as proposed against v1 as other call
      sites depend explicitly setting flags to 0.
 - patch 2:
    - Moved large_next[] array into percpu_cluster to make it per-cpu
      (recommended by Huang, Ying).
    - large_next[] array is dynamically allocated because PMD_ORDER is not
      compile-time constant for powerpc (fixes build error).


Thanks,
Ryan

P.S. I know we agreed this is not a prerequisite for merging small-sized THP,
but given Huang Ying had provided some review feedback, I wanted to progress it.
All the actual prerequisites are either complete or being worked on by others.


[1] https://lore.kernel.org/linux-mm/20231010142111.3997780-1-ryan.roberts@arm.com/
[2] https://lore.kernel.org/linux-mm/20231017161302.2518826-1-ryan.roberts@arm.com/
[3] https://lore.kernel.org/linux-mm/15a52c3d-9584-449b-8228-1335e0753b04@arm.com/


Ryan Roberts (4):
  mm: swap: Remove CLUSTER_FLAG_HUGE from swap_cluster_info:flags
  mm: swap: Remove struct percpu_cluster
  mm: swap: Simplify ssd behavior when scanner steals entry
  mm: swap: Swap-out small-sized THP without splitting

 include/linux/swap.h |  31 +++---
 mm/huge_memory.c     |   3 -
 mm/swapfile.c        | 232 ++++++++++++++++++++++++-------------------
 mm/vmscan.c          |  10 +-
 4 files changed, 149 insertions(+), 127 deletions(-)

--
2.25.1



             reply	other threads:[~2023-10-25 14:46 UTC|newest]

Thread overview: 116+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-25 14:45 Ryan Roberts [this message]
2023-10-25 14:45 ` [PATCH v3 1/4] mm: swap: Remove CLUSTER_FLAG_HUGE from swap_cluster_info:flags Ryan Roberts
2024-02-22 10:19   ` David Hildenbrand
2024-02-22 10:20     ` David Hildenbrand
2024-02-26 17:41       ` Ryan Roberts
2024-02-27 17:10         ` Ryan Roberts
2024-02-27 19:17           ` David Hildenbrand
2024-02-28  9:37             ` Ryan Roberts
2024-02-28 12:12               ` David Hildenbrand
2024-02-28 14:57                 ` Ryan Roberts
2024-02-28 15:12                   ` David Hildenbrand
2024-02-28 15:18                     ` Ryan Roberts
2024-03-01 16:27                     ` Ryan Roberts
2024-03-01 16:31                       ` Matthew Wilcox
2024-03-01 16:44                         ` Ryan Roberts
2024-03-01 17:00                           ` David Hildenbrand
2024-03-01 17:14                             ` Ryan Roberts
2024-03-01 17:18                               ` David Hildenbrand
2024-03-01 17:06                           ` Ryan Roberts
2024-03-04  4:52                             ` Barry Song
2024-03-04  5:42                               ` Barry Song
2024-03-05  7:41                                 ` Ryan Roberts
2024-03-01 16:31                       ` Ryan Roberts
2024-03-01 16:32                       ` David Hildenbrand
2024-03-04 16:03                 ` Ryan Roberts
2024-03-04 17:30                   ` David Hildenbrand
2024-03-04 18:38                     ` Ryan Roberts
2024-03-04 20:50                       ` David Hildenbrand
2024-03-04 21:55                         ` Ryan Roberts
2024-03-04 22:02                           ` David Hildenbrand
2024-03-04 22:34                             ` Ryan Roberts
2024-03-05  6:11                               ` Huang, Ying
2024-03-05  8:35                                 ` David Hildenbrand
2024-03-05  8:46                                   ` Ryan Roberts
2024-02-28 13:33               ` Matthew Wilcox
2024-02-28 14:24                 ` Ryan Roberts
2024-02-28 14:59                   ` Ryan Roberts
2023-10-25 14:45 ` [PATCH v3 2/4] mm: swap: Remove struct percpu_cluster Ryan Roberts
2023-10-25 14:45 ` [PATCH v3 3/4] mm: swap: Simplify ssd behavior when scanner steals entry Ryan Roberts
2023-10-25 14:45 ` [PATCH v3 4/4] mm: swap: Swap-out small-sized THP without splitting Ryan Roberts
2023-10-30  8:18   ` Huang, Ying
2023-10-30 13:59     ` Ryan Roberts
2023-10-31  8:12       ` Huang, Ying
2023-11-03 11:42         ` Ryan Roberts
2023-11-02  7:40   ` Barry Song
2023-11-02 10:21     ` Ryan Roberts
2023-11-02 22:36       ` Barry Song
2023-11-03 11:31         ` Ryan Roberts
2023-11-03 13:57           ` Steven Price
2023-11-04  9:34             ` Barry Song
2023-11-06 10:12               ` Steven Price
2023-11-06 21:39                 ` Barry Song
2023-11-08 11:51                   ` Steven Price
2023-11-07 12:46               ` Ryan Roberts
2023-11-07 18:05                 ` Barry Song
2023-11-08 11:23                   ` Barry Song
2023-11-08 20:20                     ` Ryan Roberts
2023-11-08 21:04                       ` Barry Song
2023-11-04  5:49           ` Barry Song
2024-02-05  9:51   ` Barry Song
2024-02-05 12:14     ` Ryan Roberts
2024-02-18 23:40       ` Barry Song
2024-02-20 20:03         ` Ryan Roberts
2024-03-05  9:00         ` Ryan Roberts
2024-03-05  9:54           ` Barry Song
2024-03-05 10:44             ` Ryan Roberts
2024-02-27 12:28     ` Ryan Roberts
2024-02-27 13:37     ` Ryan Roberts
2024-02-28  2:46       ` Barry Song
2024-02-22  7:05   ` Barry Song
2024-02-22 10:09     ` David Hildenbrand
2024-02-23  9:46       ` Barry Song
2024-02-27 12:05         ` Ryan Roberts
2024-02-28  1:23           ` Barry Song
2024-02-28  9:34             ` David Hildenbrand
2024-02-28 23:18               ` Barry Song
2024-02-28 15:57             ` Ryan Roberts
2023-11-29  7:47 ` [PATCH v3 0/4] " Barry Song
2023-11-29 12:06   ` Ryan Roberts
2023-11-29 20:38     ` Barry Song
2024-01-18 11:10 ` [PATCH RFC 0/6] mm: support large folios swap-in Barry Song
2024-01-18 11:10   ` [PATCH RFC 1/6] arm64: mm: swap: support THP_SWAP on hardware with MTE Barry Song
2024-01-26 23:14     ` Chris Li
2024-02-26  2:59       ` Barry Song
2024-01-18 11:10   ` [PATCH RFC 2/6] mm: swap: introduce swap_nr_free() for batched swap_free() Barry Song
2024-01-26 23:17     ` Chris Li
2024-02-26  4:47       ` Barry Song
2024-01-18 11:10   ` [PATCH RFC 3/6] mm: swap: make should_try_to_free_swap() support large-folio Barry Song
2024-01-26 23:22     ` Chris Li
2024-01-18 11:10   ` [PATCH RFC 4/6] mm: support large folios swapin as a whole Barry Song
2024-01-27 19:53     ` Chris Li
2024-02-26  7:29       ` Barry Song
2024-01-27 20:06     ` Chris Li
2024-02-26  7:31       ` Barry Song
2024-01-18 11:10   ` [PATCH RFC 5/6] mm: rmap: weaken the WARN_ON in __folio_add_anon_rmap() Barry Song
2024-01-18 11:54     ` David Hildenbrand
2024-01-23  6:49       ` Barry Song
2024-01-29  3:25         ` Chris Li
2024-01-29 10:06           ` David Hildenbrand
2024-01-29 16:31             ` Chris Li
2024-02-26  5:05               ` Barry Song
2024-04-06 23:27             ` Barry Song
2024-01-27 23:41     ` Chris Li
2024-01-18 11:10   ` [PATCH RFC 6/6] mm: madvise: don't split mTHP for MADV_PAGEOUT Barry Song
2024-01-29  2:15     ` Chris Li
2024-02-26  6:39       ` Barry Song
2024-02-27 12:22     ` Ryan Roberts
2024-02-27 22:39       ` Barry Song
2024-02-27 14:40     ` Ryan Roberts
2024-02-27 18:57       ` Barry Song
2024-02-28  3:49         ` Barry Song
2024-01-18 15:25   ` [PATCH RFC 0/6] mm: support large folios swap-in Ryan Roberts
2024-01-18 23:54     ` Barry Song
2024-01-19 13:25       ` Ryan Roberts
2024-01-27 14:27         ` Barry Song
2024-01-29  9:05   ` Huang, Ying

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