From: Matthew Wilcox <willy@infradead.org>
To: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
"Andrew Morton" <akpm@linux-foundation.org>,
김성훈 <sfoon.kim@samsung.com>, "Song Liu" <songliubraving@fb.com>,
"Rik van Riel" <riel@surriel.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
"Johannes Weiner" <hannes@cmpxchg.org>,
"Hillf Danton" <hdanton@sina.com>,
"Hugh Dickins" <hughd@google.com>,
"William Kucharski" <william.kucharski@oracle.com>,
"Oleg Nesterov" <oleg@redhat.com>,
"Yang Shi" <yang.shi@linux.alibaba.com>
Subject: Re: [PATCH] mm/thp: decrease nr_thps in file's mapping on THP split
Date: Wed, 13 Oct 2021 13:01:40 +0100 [thread overview]
Message-ID: <YWbKpH3vroAF7yw4@casper.infradead.org> (raw)
In-Reply-To: <5eafae55-f207-38a8-d6d3-8bda74ae9c60@samsung.com>
On Wed, Oct 13, 2021 at 12:47:03PM +0200, Marek Szyprowski wrote:
> On 12.10.2021 14:43, Matthew Wilcox wrote:
> > On Tue, Oct 12, 2021 at 02:02:37PM +0200, Marek Szyprowski wrote:
> >> Decrease nr_thps counter in file's mapping to ensure that the page cache
> >> won't be dropped excessively on file write access if page has been
> >> already splitted.
> >>
> >> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> >> Fixes: 09d91cda0e82 ("mm,thp: avoid writes to file with THP in pagecache")
> >> Fixes: 06d3eff62d9d ("mm/thp: fix node page state in split_huge_page_to_list()")
> >> ---
> >> I've analyzed the code a few times but either I missed something or the
> >> nr_thps counter is not decremented during the THP split on non-shmem file
> >> pages.
> > This looks OK to me, but have you tested it? If so, what workload did
> > you use? The way you wrote this changelog makes it sound like you only
> > read the code and there have been rather too many bugs introduced recently
> > that way :-(
>
> Well, indeed I've found it while reading the code. However I've just
> tried a test scenario, where one runs a big binary, kernel remaps it
> with THPs, then one forces THP split with
> /sys/kernel/debug/split_huge_pages. During any further open of that
> binary with O_RDWR or O_WRITEONLY kernel drops page cache for it,
> because of non-zero thps counter.
... and with this patch, it no longer happens? Good enough for me!
Acked-by: Matthew Wilcox (Oracle) <willy@infradead.org>
next prev parent reply other threads:[~2021-10-13 12:03 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20211012120247eucas1p1f66926c6fc334216cdbdd39285601aa8@eucas1p1.samsung.com>
2021-10-12 12:02 ` [PATCH] mm/thp: decrease nr_thps in file's mapping on THP split Marek Szyprowski
2021-10-12 12:43 ` Matthew Wilcox
2021-10-13 10:47 ` Marek Szyprowski
2021-10-13 12:01 ` Matthew Wilcox [this message]
2021-10-13 21:44 ` Yang Shi
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