From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andrea Arcangeli <aarcange@redhat.com>, Zi Yan <ziy@nvidia.com>,
Yang Shi <yang.shi@linux.alibaba.com>,
Ralph Campbell <rcampbell@nvidia.com>,
John Hubbard <jhubbard@nvidia.com>,
William Kucharski <william.kucharski@oracle.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCHv4 4/8] khugepaged: Drain LRU add pagevec after swapin
Date: Fri, 17 Apr 2020 17:59:09 +0300 [thread overview]
Message-ID: <20200417145909.476o5ppho5p3cgyk@box> (raw)
In-Reply-To: <20200416214145.bfbb1afcc7a632e8cafdf203@linux-foundation.org>
On Thu, Apr 16, 2020 at 09:41:45PM -0700, Andrew Morton wrote:
> On Thu, 16 Apr 2020 19:00:22 +0300 "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> wrote:
>
> > __collapse_huge_page_isolate() may fail due to extra pin in the LRU add
> > pagevec. It's pretty common for swapin case: we swap in pages just to
> > fail due to the extra pin.
> >
> > Drain LRU add pagevec on successful swapin.
>
> I don't see how this patch can do anything to prevent
> __collapse_huge_page_isolate() from failing, which is what the
> changelog implies.
>
> Can we have a more detailed changelog, please?
What about something like this:
khugepaged: Drain LRU add pagevec after swapin
collapse_huge_page() tries to swap in pages that are part of the PMD
range. Just swapped in page goes though LRU add cache. The cache gets
extra reference on the page.
The extra reference can lead to the collapse fail: the following
__collapse_huge_page_isolate() would check refcount and abort collapse
seeing unexpected refcount.
The fix is to drain local LRU add cache in __collapse_huge_page_swapin()
if we successfully swapped in any pages.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-and-Tested-by: Zi Yan <ziy@nvidia.com>
Acked-by: Yang Shi <yang.shi@linux.alibaba.com>
--
Kirill A. Shutemov
next prev parent reply other threads:[~2020-04-17 14:59 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-16 16:00 [PATCHv4 0/8] thp/khugepaged improvements and CoW semantics Kirill A. Shutemov
2020-04-16 16:00 ` [PATCHv4 1/8] khugepaged: Add self test Kirill A. Shutemov
2020-04-16 16:00 ` [PATCHv4 2/8] khugepaged: Do not stop collapse if less than half PTEs are referenced Kirill A. Shutemov
2020-04-16 16:00 ` [PATCHv4 3/8] khugepaged: Drain all LRU caches before scanning pages Kirill A. Shutemov
2020-04-16 16:00 ` [PATCHv4 4/8] khugepaged: Drain LRU add pagevec after swapin Kirill A. Shutemov
2020-04-17 4:41 ` Andrew Morton
2020-04-17 14:59 ` Kirill A. Shutemov [this message]
2020-04-16 16:00 ` [PATCHv4 5/8] khugepaged: Allow to collapse a page shared across fork Kirill A. Shutemov
2020-04-16 16:00 ` [PATCHv4 6/8] khugepaged: Allow to collapse PTE-mapped compound pages Kirill A. Shutemov
2020-04-16 16:00 ` [PATCHv4 7/8] thp: Change CoW semantics for anon-THP Kirill A. Shutemov
2020-04-21 0:48 ` [thp] fd80f22b29: vm-scalability.median 10.3% improvement kernel test robot
2020-04-21 0:48 ` kernel test robot
2020-04-16 16:00 ` [PATCHv4 8/8] khugepaged: Introduce 'max_ptes_shared' tunable Kirill A. Shutemov
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