linux-kernel - Re: [RFC][PATCH 2/4] printk: offload printing from wake_up_klogd_work

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Message-ID: <20170323090042.GA376@jagdpanzerIV.localdomain>
Date:   Thu, 23 Mar 2017 18:00:42 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [RFC][PATCH 2/4] printk: offload printing from
 wake_up_klogd_work_func()

On (03/20/17 17:09), Petr Mladek wrote:
[..]
> 
> BTW: wake_up_klogd_work does not need to be per-CPU as well.
> irq_work infrastructure heavily uses per-CPU variables.
> But a global struct irq_work is safe, see irq_work_claim().

so I have a patch that turns wake_up_klogd_work into a global variable,
out of curiosity, but I'm not entire sure about it. the sort of a problem
is that queued irq_works still go into a per-CPU run_lists.  per-CPU
wake_up_klogd_work permits us to queue irq work on several CPUs so we
might have better chances to execute wake_up_klogd_work_func(), while
global wake_up_klogd_work will be only in one run_list. this can defer
wake_up_klogd_work processing until that particular single CPU handles
its interrupt and calls irq_work_run_list(). what do you think?

	-ss