From: David Hildenbrand <david@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org,
David Hildenbrand <david@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@techsingularity.net>,
Dave Chinner <david@fromorbit.com>, Nadav Amit <namit@vmware.com>,
Peter Xu <peterx@redhat.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Hugh Dickins <hughd@google.com>, Vlastimil Babka <vbabka@suse.cz>,
Michael Ellerman <mpe@ellerman.id.au>,
Nicholas Piggin <npiggin@gmail.com>,
Mike Rapoport <rppt@kernel.org>,
Anshuman Khandual <anshuman.khandual@arm.com>
Subject: [PATCH RFC 0/5] mm/autonuma: replace savedwrite infrastructure
Date: Mon, 26 Sep 2022 17:26:13 +0200 [thread overview]
Message-ID: <20220926152618.194810-1-david@redhat.com> (raw)
As discussed in my talk at LPC, we can reuse the same mechanism for
deciding whether to map a pte writable when upgrading permissions via
mprotect() -- e.g., PROT_READ -> PROT_READ|PROT_WRITE -- to replace the
savedwrite infrastructure used for NUMA hinting faults (e.g., PROT_NONE
-> PROT_READ|PROT_WRITE). Instead of maintaining previous write permissions
for a pte/pmd, we re-determine if the pte/pmd can be writable.
The big benefit is that we have a common logic for deciding whether we can
map a pte/pmd writable on protection changes.
For private mappings, there should be no difference -- from
what I understand, that is what autonuma benchmarks care about.
I ran autonumabench on a system with 2 NUMA nodes, 96 GiB each via:
perf stat --null --repeat 10
The numa1 benchmark is quite noisy in my environment. I suspect that there
is no actual change in performance, even though the numbers indicate that
this series might improve performance slightly.
numa1:
mm-stable: 156.75 +- 11.67 seconds time elapsed ( +- 7.44% )
mm-stable++: 147.50 +- 9.35 seconds time elapsed ( +- 6.34% )
numa2:
mm-stable: 15.9834 +- 0.0589 seconds time elapsed ( +- 0.37% )
mm-stable++: 16.1467 +- 0.0946 seconds time elapsed ( +- 0.59% )
It is worth noting that for shared writable mappings that require
writenotify, we will only avoid write faults if the pte/pmd is dirty
(inherited from the older mprotect logic). If we ever care about optimizing
that further, we'd need a different mechanism to identify whether the FS
still needs to get notified on the next write access. In any case, such an
optimiztion will then not be autonuma-specific, but mprotect() permission
upgrades would similarly benefit from it.
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
David Hildenbrand (4):
mm/mprotect: minor can_change_pte_writable() cleanups
mm/huge_memory: try avoiding write faults when changing PMD protection
mm/autonuma: use can_change_(pte|pmd)_writable() to replace savedwrite
mm: remove unused savedwrite infrastructure
Nadav Amit (1):
mm/mprotect: allow clean exclusive anon pages to be writable
arch/powerpc/include/asm/book3s/64/pgtable.h | 80 +-------------------
arch/powerpc/kvm/book3s_hv_rm_mmu.c | 2 +-
include/linux/mm.h | 2 +
include/linux/pgtable.h | 24 ------
mm/debug_vm_pgtable.c | 32 --------
mm/huge_memory.c | 66 ++++++++++++----
mm/ksm.c | 9 +--
mm/memory.c | 19 ++++-
mm/mprotect.c | 23 +++---
9 files changed, 93 insertions(+), 164 deletions(-)
--
2.37.3
next reply other threads:[~2022-09-26 15:26 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-26 15:26 David Hildenbrand [this message]
2022-09-26 15:26 ` [PATCH RFC 1/5] mm/mprotect: allow clean exclusive anon pages to be writable David Hildenbrand
2022-09-26 15:26 ` [PATCH RFC 2/5] mm/mprotect: minor can_change_pte_writable() cleanups David Hildenbrand
2022-09-26 15:26 ` [PATCH RFC 3/5] mm/huge_memory: try avoiding write faults when changing PMD protection David Hildenbrand
2022-09-26 15:26 ` [PATCH RFC 4/5] mm/autonuma: use can_change_(pte|pmd)_writable() to replace savedwrite David Hildenbrand
2022-09-26 15:26 ` [PATCH RFC 5/5] mm: remove unused savedwrite infrastructure David Hildenbrand
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