From: Michal Hocko <mhocko@kernel.org>
To: Oleksandr Natalenko <oleksandr@redhat.com>
Cc: linux-kernel@vger.kernel.org, Kirill Tkhai <ktkhai@virtuozzo.com>,
Vlastimil Babka <vbabka@suse.cz>,
Matthew Wilcox <willy@infradead.org>,
Pavel Tatashin <pasha.tatashin@soleen.com>,
Timofey Titovets <nefelim4ag@gmail.com>,
Aaron Tomlin <atomlin@redhat.com>,
Grzegorz Halat <ghalat@redhat.com>,
linux-mm@kvack.org, linux-api@vger.kernel.org
Subject: Re: [PATCH RFC v2 0/4] mm/ksm: add option to automerge VMAs
Date: Tue, 14 May 2019 16:41:05 +0200 [thread overview]
Message-ID: <20190514144105.GF4683@dhcp22.suse.cz> (raw)
In-Reply-To: <20190514131654.25463-1-oleksandr@redhat.com>
[This is adding a new user visible interface so you should be CCing
linux-api mailing list. Also CC Hugh for KSM in general. Done now]
On Tue 14-05-19 15:16:50, Oleksandr Natalenko wrote:
> By default, KSM works only on memory that is marked by madvise(). And the
> only way to get around that is to either:
>
> * use LD_PRELOAD; or
> * patch the kernel with something like UKSM or PKSM.
>
> Instead, lets implement a sysfs knob, which allows marking VMAs as
> mergeable. This can be used manually on some task in question or by some
> small userspace helper daemon.
>
> The knob is named "force_madvise", and it is write-only. It accepts a PID
> to act on. To mark the VMAs as mergeable, use:
>
> # echo PID > /sys/kernel/mm/ksm/force_madvise
>
> To unmerge all the VMAs, use the same approach, prepending the PID with
> the "minus" sign:
>
> # echo -PID > /sys/kernel/mm/ksm/force_madvise
>
> This patchset is based on earlier Timofey's submission [1], but it doesn't
> use dedicated kthread to walk through the list of tasks/VMAs. Instead,
> it is up to userspace to traverse all the tasks in /proc if needed.
>
> The previous suggestion [2] was based on amending do_anonymous_page()
> handler to implement fully automatic mode, but this approach was
> incorrect due to improper locking and not desired due to excessive
> complexity.
>
> The current approach just implements minimal interface and leaves the
> decision on how and when to act to userspace.
Please make sure to describe a usecase that warrants adding a new
interface we have to maintain for ever.
>
> Thanks.
>
> [1] https://lore.kernel.org/patchwork/patch/1012142/
> [2] http://lkml.iu.edu/hypermail/linux/kernel/1905.1/02417.html
>
> Oleksandr Natalenko (4):
> mm/ksm: introduce ksm_enter() helper
> mm/ksm: introduce ksm_leave() helper
> mm/ksm: introduce force_madvise knob
> mm/ksm: add force merging/unmerging documentation
>
> Documentation/admin-guide/mm/ksm.rst | 11 ++
> mm/ksm.c | 160 +++++++++++++++++++++------
> 2 files changed, 137 insertions(+), 34 deletions(-)
>
> --
> 2.21.0
>
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-05-14 14:41 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-14 13:16 [PATCH RFC v2 0/4] mm/ksm: add option to automerge VMAs Oleksandr Natalenko
2019-05-14 13:16 ` [PATCH RFC v2 1/4] mm/ksm: introduce ksm_enter() helper Oleksandr Natalenko
2019-05-14 13:16 ` [PATCH RFC v2 2/4] mm/ksm: introduce ksm_leave() helper Oleksandr Natalenko
2019-05-14 13:16 ` [PATCH RFC v2 3/4] mm/ksm: introduce force_madvise knob Oleksandr Natalenko
2019-05-14 13:22 ` Aaron Tomlin
2019-05-15 0:48 ` Timofey Titovets
2019-05-14 13:16 ` [PATCH RFC v2 4/4] mm/ksm: add force merging/unmerging documentation Oleksandr Natalenko
2019-05-15 0:53 ` Timofey Titovets
2019-05-15 6:26 ` Oleksandr Natalenko
2019-05-14 14:41 ` Michal Hocko [this message]
2019-05-14 14:51 ` [PATCH RFC v2 0/4] mm/ksm: add option to automerge VMAs Michal Hocko
2019-05-15 6:25 ` Oleksandr Natalenko
2019-05-15 6:53 ` Michal Hocko
2019-05-15 7:37 ` Oleksandr Natalenko
2019-05-15 8:33 ` Michal Hocko
2019-05-15 8:51 ` Oleksandr Natalenko
2019-05-15 14:24 ` Michal Hocko
2019-05-15 14:51 ` Michal Hocko
2019-05-15 15:15 ` Greg KH
2019-05-16 7:47 ` Michal Hocko
2019-05-16 7:53 ` Greg KH
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