linux-kernel - Re: [PATCH v2] signals: Avoid unnecessary taking of sighand->siglock

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Message-ID: <a0233360-919e-4587-1c56-84b944cd6779@list.ru>
Date:   Fri, 23 Sep 2016 22:43:55 +0300
From:   Stas Sergeev <stsp@...t.ru>
To:     Waiman Long <Waiman.Long@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org,
        Scott J Norton <scott.norton@....com>,
        Douglas Hatch <doug.hatch@....com>
Subject: Re: [PATCH v2] signals: Avoid unnecessary taking of sighand->siglock

23.09.2016 19:56, Waiman Long пишет:
> When running certain database workload on a high-end system with many
> CPUs, it was found that spinlock contention in the sigprocmask syscalls
> became a significant portion of the overall CPU cycles as shown below.
Hi, I was recently facing the same problem, and my solution
was to extract swapcontext() from libtask - it has better semantic
and does not do sigprocmask. How much you hack sigprocmask,
it is still faster to just not call it at all.
Alternatively, perhaps the speed-up can be achieved if the
current mask is exported to glibc via vdso.
Just my 2 cents.