From: Vlastimil Babka <vbabka@suse.cz>
To: Rik van Riel <riel@surriel.com>, hughd@google.com
Cc: xuyu@linux.alibaba.com, akpm@linux-foundation.org,
mgorman@suse.de, aarcange@redhat.com, willy@infradead.org,
linux-kernel@vger.kernel.org, kernel-team@fb.com,
linux-mm@kvack.org, mhocko@suse.com
Subject: Re: [PATCH 3/3] mm,thp,shmem: make khugepaged obey tmpfs mount flags
Date: Thu, 26 Nov 2020 20:42:11 +0100 [thread overview]
Message-ID: <cc08c0b4-84b3-5aa0-4c96-03f3767eec56@suse.cz> (raw)
In-Reply-To: <8f2428a049f2c29f092782699bcb3af76bf72b6a.camel@surriel.com>
On 11/26/20 7:14 PM, Rik van Riel wrote:
> On Thu, 2020-11-26 at 18:18 +0100, Vlastimil Babka wrote:
>> On 11/24/20 8:49 PM, Rik van Riel wrote:
>>> Currently if thp enabled=[madvise], mounting a tmpfs filesystem
>>> with huge=always and mmapping files from that tmpfs does not
>>> result in khugepaged collapsing those mappings, despite the
>>> mount flag indicating that it should.
>>>
>>> Fix that by breaking up the blocks of tests in hugepage_vma_check
>>> a little bit, and testing things in the correct order.
>>>
>>> Signed-off-by: Rik van Riel <riel@surriel.com>
>>> Fixes: c2231020ea7b ("mm: thp: register mm for khugepaged when
>>> merging vma for shmem")
>>
>> Looks ok. But, it we have sysfs thp enabled=never, and shmem mount
>> explicitly
>> thp enabled, then shmem mount overrides the global sysfs setting and
>> thp's will
>> be allocated there, right? However, khugepaged_enabled() will be
>> false and thus
>> khugepaged won't run at all? So a similar situation than what you're
>> fixing here.
>
> Indeed, that is somewhat similar. Whether or not shmem
> allocations attempt huge pages is controlled by both
> the file /sys/kernel/mm/transparent_hugepage/shmem_enabled
Ah right, there's also that sysfs file.
> and mount options.
>
> This patch makes khugepaged treat the mount options
> and/or
> sysfs flag as enabling collapsing of huge pages in case
> enabled = [always] for regular THPs.
>
> Should I send another patch on top
> of this that causes
> khugepaged to be enabled when regular THPs are disabled,
> but shmem THPs are enabled in any way?
I think it would make sense. Although it might involve counting
thp-enabled shmem mounts and only run khugepaged when there are >0 of them.
next prev parent reply other threads:[~2020-11-26 19:47 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-24 19:49 [PATCH v6 0/3] mm,thp,shm: limit shmem THP alloc gfp_mask Rik van Riel
2020-11-24 19:49 ` [PATCH 1/3] mm,thp,shmem: " Rik van Riel
2020-11-26 16:56 ` Vlastimil Babka
2020-11-27 8:15 ` Michal Hocko
2020-11-24 19:49 ` [PATCH 2/3] mm,thp,shm: limit gfp mask to no more than specified Rik van Riel
2020-11-26 13:40 ` Michal Hocko
2020-11-26 18:04 ` Rik van Riel
2020-11-27 7:52 ` Michal Hocko
2020-11-27 19:03 ` Rik van Riel
2020-11-30 10:00 ` Michal Hocko
2020-11-30 14:40 ` Rik van Riel
2020-11-24 19:49 ` [PATCH 3/3] mm,thp,shmem: make khugepaged obey tmpfs mount flags Rik van Riel
2020-11-26 17:18 ` Vlastimil Babka
2020-11-26 18:14 ` Rik van Riel
2020-11-26 19:42 ` Vlastimil Babka [this message]
2020-11-26 20:14 ` Rik van Riel
2020-12-14 21:16 ` [PATCH v6 0/3] mm,thp,shm: limit shmem THP alloc gfp_mask Hugh Dickins
2020-12-14 22:20 ` Andrew Morton
2020-12-14 22:52 ` Vlastimil Babka
2021-02-24 8:41 ` Hugh Dickins
2021-02-24 14:46 ` Rik van Riel
2021-02-24 16:55 ` Hugh Dickins
2021-02-24 17:10 ` [PATCH 4/3] mm,shmem,thp: limit shmem THP allocations to requested zones Rik van Riel
2021-02-26 12:34 ` Vlastimil Babka
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