linux-kernel - Re: [PATCH v3] pipe: use __pipe_{lock,unlock} instead of spinlock

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Message-ID: <Y8TUqcSO5VrbYfcM@casper.infradead.org>
Date:   Mon, 16 Jan 2023 04:38:01 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     maobibo <maobibo@...ngson.cn>
Cc:     Hongchen Zhang <zhanghongchen@...ngson.cn>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Howells <dhowells@...hat.com>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        "Christian Brauner (Microsoft)" <brauner@...nel.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] pipe: use __pipe_{lock,unlock} instead of spinlock

On Mon, Jan 16, 2023 at 11:16:13AM +0800, maobibo wrote:
> Hongchen,
> 
> I have a glance with this patch, it simply replaces with
> spinlock_irqsave with mutex lock. There may be performance
> improvement with two processes competing with pipe, however
> for N processes, there will be complex context switches
> and ipi interruptts.
> 
> Can you find some cases with more than 2 processes competing
> pipe, rather than only unixbench?

What real applications have pipes with more than 1 writer & 1 reader?
I'm OK with slowing down the weird cases if the common cases go faster.