linux-kernel - Re: Very slow SYS_io

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Message-ID: <x49fu0a3rz1.fsf@segfault.boston.devel.redhat.com>
Date:   Mon, 23 Jul 2018 11:13:38 -0400
From:   Jeff Moyer <jmoyer@...hat.com>
To:     Alex Richman <alex.r@...abs.co.uk>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: Very slow SYS_io_destroy()

Alex Richman <alex.r@...abs.co.uk> writes:

> Hi,
>
> I'm seeing some weirdness with AIO, specifically SYS_io_destroy() is
> taking upwards of ~100000 microseconds (~100 miliseconds) per call.
> How long is that call expected to take?  I can see from the source

Well, it waits for an RCU grace period.  I would not expect that to take
100ms, though.  What kernel version is this?

-Jeff