From: Al Viro <viro@zeniv.linux.org.uk>
To: Manish Varma <varmam@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@android.com, Kelly Rossmoyer <krossmo@google.com>
Subject: Re: [PATCH v2] fs: Improve eventpoll logging to stop indicting timerfd
Date: Thu, 1 Apr 2021 02:28:55 +0000 [thread overview]
Message-ID: <YGUv5yIBTFbwuTxB@zeniv-ca.linux.org.uk> (raw)
In-Reply-To: <20210401021645.2609047-1-varmam@google.com>
On Wed, Mar 31, 2021 at 07:16:45PM -0700, Manish Varma wrote:
> timerfd doesn't create any wakelocks, but eventpoll can. When it does,
> it names them after the underlying file descriptor, and since all
> timerfd file descriptors are named "[timerfd]" (which saves memory on
> systems like desktops with potentially many timerfd instances), all
> wakesources created as a result of using the eventpoll-on-timerfd idiom
> are called... "[timerfd]".
>
> However, it becomes impossible to tell which "[timerfd]" wakesource is
> affliated with which process and hence troubleshooting is difficult.
>
> This change addresses this problem by changing the way eventpoll
> wakesources are named:
>
> 1) the top-level per-process eventpoll wakesource is now named "epoll:P"
> (instead of just "eventpoll"), where P, is the PID of the creating
> process.
> 2) individual per-underlying-filedescriptor eventpoll wakesources are
> now named "epollitemN:P.F", where N is a unique ID token and P is PID
> of the creating process and F is the name of the underlying file
> descriptor.
>
> All together that should be splitted up into a change to eventpoll and
> timerfd (or other file descriptors).
FWIW, it smells like a variant of wakeup_source_register() that would
take printf format + arguments would be a good idea. I.e. something
like
> + snprintf(buf, sizeof(buf), "epoll:%d", task_pid);
> + epi->ep->ws = wakeup_source_register(NULL, buf);
... = wakeup_source_register(NULL, "epoll:%d", task_pid);
etc.
next prev parent reply other threads:[~2021-04-01 2:29 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-01 2:16 [PATCH v2] fs: Improve eventpoll logging to stop indicting timerfd Manish Varma
2021-04-01 2:28 ` Al Viro [this message]
2021-04-01 23:57 ` Manish Varma
2021-04-01 6:44 ` kernel test robot
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