From: Matthew Wilcox <willy@infradead.org>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
Shakeel Butt <shakeelb@google.com>,
John Hubbard <jhubbard@nvidia.com>,
Jason Gunthorpe <jgg@nvidia.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Mike Rapoport <rppt@linux.ibm.com>,
Yang Shi <shy828301@gmail.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Vlastimil Babka <vbabka@suse.cz>, Jann Horn <jannh@google.com>,
Michal Hocko <mhocko@kernel.org>, Nadav Amit <namit@vmware.com>,
Rik van Riel <riel@surriel.com>, Roman Gushchin <guro@fb.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Peter Xu <peterx@redhat.com>, Donald Dutile <ddutile@redhat.com>,
Christoph Hellwig <hch@lst.de>, Oleg Nesterov <oleg@redhat.com>,
Jan Kara <jack@suse.cz>, Liang Zhang <zhangliang5@huawei.com>,
linux-mm@kvack.org, Nadav Amit <nadav.amit@gmail.com>
Subject: Re: [PATCH RFC v2 1/9] mm: optimize do_wp_page() for exclusive pages in the swapcache
Date: Wed, 26 Jan 2022 14:25:25 +0000 [thread overview]
Message-ID: <YfFZ1SruNMubhJLo@casper.infradead.org> (raw)
In-Reply-To: <20220126095557.32392-2-david@redhat.com>
On Wed, Jan 26, 2022 at 10:55:49AM +0100, David Hildenbrand wrote:
> Liang Zhang reported [1] that the current COW logic in do_wp_page() is
> sub-optimal when it comes to swap+read fault+write fault of anonymous
> pages that have a single user, visible via a performance degradation in
> the redis benchmark. Something similar was previously reported [2] by
> Nadav with a simple reproducer.
>
> Let's optimize for pages that have been added to the swapcache but only
> have an exclusive owner. Try removing the swapcache reference if there is
> hope that we're the exclusive user.
>
> We will fail removing the swapcache reference in two scenarios:
> (1) There are additional swap entries referencing the page: copying
> instead of reusing is the right thing to do.
> (2) The page is under writeback: theoretically we might be able to reuse
> in some cases, however, we cannot remove the additional reference
> and will have to copy.
>
> Further, we might have additional references from the LRU pagevecs,
> which will force us to copy instead of being able to reuse. We'll try
> handling such references for some scenarios next. Concurrent writeback
> cannot be handled easily and we'll always have to copy.
>
> While at it, remove the superfluous page_mapcount() check: it's
> implicitly covered by the page_count() for ordinary anon pages.
>
> [1] https://lkml.kernel.org/r/20220113140318.11117-1-zhangliang5@huawei.com
> [2] https://lkml.kernel.org/r/0480D692-D9B2-429A-9A88-9BBA1331AC3A@gmail.com
>
> Reported-by: Liang Zhang <zhangliang5@huawei.com>
> Reported-by: Nadav Amit <nadav.amit@gmail.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
next prev parent reply other threads:[~2022-01-26 14:25 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-26 9:55 [PATCH RFC v2 0/9] mm: COW fixes part 1: fix the COW security issue for THP and swap David Hildenbrand
2022-01-26 9:55 ` [PATCH RFC v2 1/9] mm: optimize do_wp_page() for exclusive pages in the swapcache David Hildenbrand
2022-01-26 14:25 ` Matthew Wilcox [this message]
2022-01-28 12:53 ` Vlastimil Babka
2022-01-28 13:44 ` David Hildenbrand
2022-01-26 9:55 ` [PATCH RFC v2 2/9] mm: optimize do_wp_page() for fresh pages in local LRU pagevecs David Hildenbrand
2022-01-26 14:31 ` Matthew Wilcox
2022-01-26 14:36 ` David Hildenbrand
2022-01-26 9:55 ` [PATCH RFC v2 3/9] mm: slightly clarify KSM logic in do_swap_page() David Hildenbrand
2022-01-26 9:55 ` [PATCH RFC v2 4/9] mm: streamline COW " David Hildenbrand
2022-01-26 9:55 ` [PATCH RFC v2 5/9] mm/huge_memory: streamline COW logic in do_huge_pmd_wp_page() David Hildenbrand
2022-01-26 20:36 ` Yang Shi
2022-01-27 8:14 ` David Hildenbrand
2022-01-26 9:55 ` [PATCH RFC v2 6/9] mm/khugepaged: remove reuse_swap_page() usage David Hildenbrand
2022-01-27 21:23 ` Yang Shi
2022-01-28 8:41 ` David Hildenbrand
2022-01-28 17:10 ` Yang Shi
2022-01-26 9:55 ` [PATCH RFC v2 7/9] mm/swapfile: remove reuse_swap_page() David Hildenbrand
2022-01-26 9:55 ` [PATCH RFC v2 8/9] mm/huge_memory: remove stale page_trans_huge_mapcount() David Hildenbrand
2022-01-26 9:55 ` [PATCH RFC v2 9/9] mm/huge_memory: remove stale locking logic from __split_huge_pmd() David Hildenbrand
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YfFZ1SruNMubhJLo@casper.infradead.org \
--to=willy@infradead.org \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=david@redhat.com \
--cc=ddutile@redhat.com \
--cc=guro@fb.com \
--cc=hch@lst.de \
--cc=hughd@google.com \
--cc=jack@suse.cz \
--cc=jannh@google.com \
--cc=jgg@nvidia.com \
--cc=jhubbard@nvidia.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
--cc=mike.kravetz@oracle.com \
--cc=nadav.amit@gmail.com \
--cc=namit@vmware.com \
--cc=oleg@redhat.com \
--cc=peterx@redhat.com \
--cc=riel@surriel.com \
--cc=rientjes@google.com \
--cc=rppt@linux.ibm.com \
--cc=shakeelb@google.com \
--cc=shy828301@gmail.com \
--cc=torvalds@linux-foundation.org \
--cc=vbabka@suse.cz \
--cc=zhangliang5@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.