linux-kernel - Re: [PATCH RESEND 0/2] enable hires timer to timeout datagram socket

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Message-ID: <20170818201854.xes246oviptinwvq@localhost>
Date:   Fri, 18 Aug 2017 22:18:54 +0200
From:   Richard Cochran <richardcochran@...il.com>
To:     Vallish Vaidyeshwara <vallish@...zon.com>
Cc:     davem@...emloft.net, shuah@...nel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, eduval@...zon.com,
        anchalag@...zon.com, tglx@...utronix.de
Subject: Re: [PATCH RESEND 0/2] enable hires timer to timeout datagram socket

On Fri, Aug 18, 2017 at 06:44:08PM +0000, Vallish Vaidyeshwara wrote:
> There has been a behavior change in 4.9 kernel with refactoring of Kernel
> timer wheel in 4.8. We have a use case wherein our datagram socket
> application is sensitive to socket timeout including long timeouts.
> 
> One of the test runs with a timeout value of 180 seconds timed out at
> 190 seconds.

So the whole premise of the new timer wheel is that long timeouts need
not be very accurate.

> Patch 1: Has core code change of enabling hires timer to timeout datagram
> 	 socket on AF_UNIX and AF_INET domain

Using hrtimers will hurt performance for most applications.  Can you
please explain your use case and why is it so important?

Thanks,
Richard