linux-kernel - Debugging problems with SCHED

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Message-ID: <AM3PR03MB1170BD7F58305B54B41F20BCDD050@AM3PR03MB1170.eurprd03.prod.outlook.com>
Date:	Wed, 25 Nov 2015 12:25:31 +0000
From:	Fabrice Triboix <fabrice.triboix@...ova.com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Debugging problems with SCHED_FIFO and CPU affinity

Dear All,

We are seeing problem with our application, which is based on Linux.
Our application has many threads and we use SCHED_FIFO for threads that must have a low latency. We also use CPU affinity to try to force an even distribution of the load.

When a given event occurs, one of the SCHED_FIFO thread stops for 83ms and this prevents the correct functionning of the application. Fortunately, this bug is 95% reproducible. Interestingly enough, the problem disappears when I do not set any thread priority and CPU affinity (but the application breaks on the long run).

I am trying to investigate the issue with ftrace, with limited success so far, and I would appreciate a bit of help. I am trying to analyse the ftrace stuff using kernelshark, and I suspect a weird interaction between the the kernel and user-land.

My first question is: Is this the right mailing list to get some help on such an issue?

Many thanks for any help!

  Fabrice Triboix

Company registration number: 08121803
Place of registration: England

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