linux-kernel - [PATCH 0/7] mm: Optimize mseal checks

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Message-ID: <20240806212808.1885309-1-pedro.falcato@gmail.com>
Date: Tue,  6 Aug 2024 22:28:01 +0100
From: Pedro Falcato <pedro.falcato@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	oliver.sang@...el.com,
	torvalds@...ux-foundation.org,
	jeffxu@...gle.com,
	Michael Ellerman <mpe@...erman.id.au>,
	Pedro Falcato <pedro.falcato@...il.com>
Subject: [PATCH 0/7] mm: Optimize mseal checks

Optimize mseal checks by removing the separate can_modify_mm() step, and
just doing checks on the individual vmas, when various operations are
themselves iterating through the tree. This provides a nice speedup.

While I was at it, I found that is_madv_discard() was completely bogus.

Note that my series ignores arch_unmap(), which seems to generally be what we're trending towards[2]. It should
be applied on top of any powerpc vdso ->close patch to avoid regressions on the PPC architecture. No other
architecture seems to use arch_unmap.

Note2: This series does not pass all mseal_tests on my end (test_seal_mremap_move_dontunmap_anyaddr fails twice). But the
top of Linus's tree does not pass these for me either (neither does my Arch Linux 6.10.2 kernel),
for some reason (mremap regression?).

will-it-scale mmap1_process[1] -t 1 results:

commit 3450fe2b574b4345e4296ccae395149e1a357fee:

min:277605 max:277605 total:277605
min:281784 max:281784 total:281784
min:277238 max:277238 total:277238
min:281761 max:281761 total:281761
min:274279 max:274279 total:274279
min:254854 max:254854 total:254854
measurement
min:269143 max:269143 total:269143
min:270454 max:270454 total:270454
min:243523 max:243523 total:243523
min:251148 max:251148 total:251148
min:209669 max:209669 total:209669
min:190426 max:190426 total:190426
min:231219 max:231219 total:231219
min:275364 max:275364 total:275364
min:266540 max:266540 total:266540
min:242572 max:242572 total:242572
min:284469 max:284469 total:284469
min:278882 max:278882 total:278882
min:283269 max:283269 total:283269
min:281204 max:281204 total:281204

After this patch set:

min:280580 max:280580 total:280580
min:290514 max:290514 total:290514
min:291006 max:291006 total:291006
min:290352 max:290352 total:290352
min:294582 max:294582 total:294582
min:293075 max:293075 total:293075
measurement
min:295613 max:295613 total:295613
min:294070 max:294070 total:294070
min:293193 max:293193 total:293193
min:291631 max:291631 total:291631
min:295278 max:295278 total:295278
min:293782 max:293782 total:293782
min:290361 max:290361 total:290361
min:294517 max:294517 total:294517
min:293750 max:293750 total:293750
min:293572 max:293572 total:293572
min:295239 max:295239 total:295239
min:292932 max:292932 total:292932
min:293319 max:293319 total:293319
min:294954 max:294954 total:294954

This was a Completely Unscientific test but seems to show there were around 5-10% gains on ops per second.

[1]: mmap1_process does mmap and munmap in a loop. I didn't bother testing multithreading cases.
[2]: https://lore.kernel.org/all/87o766iehy.fsf@mail.lhotse/
Link: https://lore.kernel.org/all/202408041602.caa0372-oliver.sang@intel.com/

Pedro Falcato (7):
  mm: Move can_modify_vma to mm/internal.h
  mm/munmap: Replace can_modify_mm with can_modify_vma
  mm/mprotect: Replace can_modify_mm with can_modify_vma
  mm/mremap: Replace can_modify_mm with can_modify_vma
  mseal: Fix is_madv_discard()
  mseal: Replace can_modify_mm_madv with a vma variant
  mm: Remove can_modify_mm()

 mm/internal.h | 30 ++++++++++++++++------
 mm/madvise.c  | 13 +++-------
 mm/mmap.c     | 36 ++++++++++-----------------
 mm/mprotect.c | 12 +++------
 mm/mremap.c   | 33 ++++++------------------
 mm/mseal.c    | 69 +++++++++++----------------------------------------
 6 files changed, 63 insertions(+), 130 deletions(-)

-- 
2.46.0