From: Suren Baghdasaryan <surenb@google.com>
To: Pavel Machek <pavel@ucw.cz>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
"Colin Cross" <ccross@google.com>,
"Sumit Semwal" <sumit.semwal@linaro.org>,
"Michal Hocko" <mhocko@suse.com>,
"Dave Hansen" <dave.hansen@intel.com>,
"Kees Cook" <keescook@chromium.org>,
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"Johannes Weiner" <hannes@cmpxchg.org>,
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"Al Viro" <viro@zeniv.linux.org.uk>,
"Randy Dunlap" <rdunlap@infradead.org>,
"Kalesh Singh" <kaleshsingh@google.com>,
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rppt@kernel.org, "Peter Zijlstra" <peterz@infradead.org>,
"Catalin Marinas" <catalin.marinas@arm.com>,
vincenzo.frascino@arm.com,
"Chinwen Chang (張錦文)" <chinwen.chang@mediatek.com>,
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"Jann Horn" <jannh@google.com>,
apopple@nvidia.com, "John Hubbard" <jhubbard@nvidia.com>,
"Yu Zhao" <yuzhao@google.com>, "Will Deacon" <will@kernel.org>,
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"Hugh Dickins" <hughd@google.com>,
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"Peter Collingbourne" <pcc@google.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
"Jens Axboe" <axboe@kernel.dk>,
legion@kernel.org, "Rolf Eike Beer" <eb@emlix.com>,
"Cyrill Gorcunov" <gorcunov@gmail.com>,
"Muchun Song" <songmuchun@bytedance.com>,
"Viresh Kumar" <viresh.kumar@linaro.org>,
"Thomas Cedeno" <thomascedeno@google.com>,
sashal@kernel.org, cxfcosmos@gmail.com,
"Rasmus Villemoes" <linux@rasmusvillemoes.dk>,
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linux-mm <linux-mm@kvack.org>,
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Subject: Re: [PATCH v10 3/3] mm: add anonymous vma name refcounting
Date: Tue, 5 Oct 2021 12:14:59 -0700 [thread overview]
Message-ID: <CAJuCfpE5JEThTMhwKPUREfSE1GYcTx4YSLoVhAH97fJH_qR0Zg@mail.gmail.com> (raw)
In-Reply-To: <20211005184211.GA19804@duo.ucw.cz>
On Tue, Oct 5, 2021 at 11:42 AM Pavel Machek <pavel@ucw.cz> wrote:
>
> On Fri 2021-10-01 13:56:57, Suren Baghdasaryan wrote:
> > While forking a process with high number (64K) of named anonymous vmas the
> > overhead caused by strdup() is noticeable. Experiments with ARM64
> Android
>
> I still believe you should simply use numbers and do the
> numbers->strings mapping in userspace. We should not need to optimize
> strdups in kernel...
Here are complications with mapping numbers to strings in the userspace:
Approach 1: hardcode number->string in some header file and let all
tools use that mapping. The issue is that whenever that mapping
changes all the tools that are using it (including 3rd party ones)
have to be rebuilt. This is not really maintainable since we don't
control 3rd party tools and even for the ones we control, it will be a
maintenance issue figuring out which version of the tool used which
header file.
Approach 2: have a centralized facility (a process or a DB)
maintaining number->string mapping. This would require an additional
request to this facility whenever we want to make a number->string
conversion. Moreover, when we want to name a VMA, we would have to
register a new VMA name in that facility or check that one already
exists and get its ID. So each prctl() call to name a VMA will be
preceded by such a request (IPC call), maybe with some optimizations
to cache already known number->string pairs. This would be quite
expensive performance-wise. Additional issue with this approach is
that this mapping will have to be persistent to handle a case when the
facility crashes and has to be restored.
As I said before, it complicates userspace quite a bit. Is that a good
enough reason to store the names in the kernel and pay a little more
memory for that? IMHO yes, but I might be wrong.
Thanks,
Suren.
>
> Best regards,
> Pavel
> --
> http://www.livejournal.com/~pavelmachek
>
> --
> To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com.
next prev parent reply other threads:[~2021-10-05 19:15 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-01 20:56 [PATCH v10 1/3] mm: rearrange madvise code to allow for reuse Suren Baghdasaryan
2021-10-01 20:56 ` [PATCH v10 2/3] mm: add a field to store names for private anonymous memory Suren Baghdasaryan
2021-10-01 23:08 ` Andrew Morton
2021-10-02 0:52 ` Suren Baghdasaryan
2021-10-04 16:21 ` Suren Baghdasaryan
2021-10-07 2:39 ` Andrew Morton
2021-10-07 2:50 ` Suren Baghdasaryan
2021-10-01 20:56 ` [PATCH v10 3/3] mm: add anonymous vma name refcounting Suren Baghdasaryan
2021-10-05 18:42 ` Pavel Machek
2021-10-05 19:14 ` Suren Baghdasaryan [this message]
2021-10-05 19:21 ` Kees Cook
2021-10-05 20:04 ` Pavel Machek
2021-10-05 20:43 ` Suren Baghdasaryan
2021-10-06 6:57 ` John Hubbard
2021-10-06 8:27 ` Michal Hocko
2021-10-06 9:27 ` David Hildenbrand
2021-10-06 15:01 ` Suren Baghdasaryan
2021-10-06 15:07 ` David Hildenbrand
2021-10-06 15:20 ` Suren Baghdasaryan
2021-10-07 2:29 ` Andrew Morton
2021-10-07 2:46 ` Suren Baghdasaryan
2021-10-07 2:53 ` Andrew Morton
2021-10-07 3:01 ` Suren Baghdasaryan
2021-10-07 7:27 ` David Hildenbrand
2021-10-07 7:33 ` David Hildenbrand
2021-10-07 15:42 ` Suren Baghdasaryan
2021-10-06 17:58 ` Pavel Machek
2021-10-06 18:18 ` Suren Baghdasaryan
2021-10-07 8:10 ` Michal Hocko
2021-10-07 8:41 ` Pavel Machek
2021-10-07 8:47 ` Rasmus Villemoes
2021-10-07 10:15 ` Pavel Machek
2021-10-07 16:04 ` Suren Baghdasaryan
2021-10-07 16:40 ` Michal Hocko
2021-10-07 16:58 ` Suren Baghdasaryan
2021-10-07 17:31 ` Michal Hocko
2021-10-07 17:50 ` Suren Baghdasaryan
2021-10-07 18:12 ` Kees Cook
2021-10-07 18:50 ` Suren Baghdasaryan
2021-10-07 19:02 ` John Hubbard
2021-10-07 21:32 ` Suren Baghdasaryan
2021-10-08 1:04 ` Liam Howlett
2021-10-08 7:25 ` Rasmus Villemoes
2021-10-08 7:43 ` David Hildenbrand
2021-10-08 21:13 ` Kees Cook
2021-10-08 6:34 ` Michal Hocko
2021-10-08 14:14 ` Dave Hansen
2021-10-08 14:57 ` Michal Hocko
2021-10-08 16:10 ` Suren Baghdasaryan
2021-10-08 20:58 ` Kees Cook
2021-10-11 8:36 ` Michal Hocko
2021-10-12 1:18 ` Suren Baghdasaryan
2021-10-12 1:20 ` Suren Baghdasaryan
2021-10-12 3:00 ` Johannes Weiner
2021-10-12 5:36 ` Suren Baghdasaryan
2021-10-12 18:26 ` Johannes Weiner
2021-10-12 18:52 ` Suren Baghdasaryan
2021-10-12 20:41 ` Johannes Weiner
2021-10-12 20:59 ` Suren Baghdasaryan
2021-10-12 7:36 ` Michal Hocko
2021-10-12 16:50 ` Suren Baghdasaryan
2021-10-12 7:43 ` David Hildenbrand
2021-10-12 17:01 ` Suren Baghdasaryan
2021-10-14 20:16 ` Suren Baghdasaryan
2021-10-15 8:03 ` David Hildenbrand
2021-10-15 16:30 ` Suren Baghdasaryan
2021-10-15 16:39 ` David Hildenbrand
2021-10-15 18:33 ` Suren Baghdasaryan
2021-10-15 17:45 ` Kees Cook
2021-10-07 7:59 ` Michal Hocko
2021-10-07 15:45 ` Suren Baghdasaryan
2021-10-07 16:37 ` Michal Hocko
2021-10-07 16:43 ` Suren Baghdasaryan
2021-10-07 17:25 ` Michal Hocko
2021-10-07 17:30 ` Suren Baghdasaryan
2021-10-04 7:03 ` [PATCH v10 1/3] mm: rearrange madvise code to allow for reuse Rolf Eike Beer
2021-10-04 16:18 ` Suren Baghdasaryan
2021-10-05 21:00 ` Liam Howlett
2021-10-05 21:30 ` Suren Baghdasaryan
2021-10-06 17:33 ` Liam Howlett
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