linux-kernel - Re: [RFC][PATCH 00/12] various perf fixes

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Date:	Mon, 15 Feb 2016 17:59:35 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Dmitry Vyukov <dvyukov@...gle.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Stephane Eranian <eranian@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>, vince@...ter.net,
	Andi Kleen <andi@...stfloor.org>, jolsa@...hat.com,
	Thomas Gleixner <tglx@...utronix.de>,
	Arnaldo Carvalho de Melo <acme@...radead.org>
Subject: Re: [RFC][PATCH 00/12] various perf fixes

On Mon, Feb 15, 2016 at 05:54:51PM +0100, Dmitry Vyukov wrote:
> > OK, now I have syz-fuzzer at ~950% CPU time and a gazillion syz-executor
> > tasks running.
> 
> If you want more or less, it is controlled by the "procs": 160 config parameter.

I've got 2*10 cores, each with SMT enabled for 40 'CPU's, 160 is the
4*NR_CPUS thing you suggested.

Should be good enough to keep the machine busy I suppose.

> > No splats yet, I'll leave it running for a while.
> >
> >
> > In order to get coverage support, I have to apply that one patch to my
> > local kernel, right?
> 
> Unfortunately you also need a very fresh gcc. Kcov support was
> committed to gcc in revision 231296 (Dec 4). So you either need to
> build gcc manually or obtain some kind of nightly build.

My last GCC build is 5.3-branch or so, is that fresh enough?

> Yes, you need to apply the kcov patch to kernel. It is now in
> linux-next tree, so you can pull from there.
> Enable CONFIG_KCOV and CONFIG_DEBUGFS and build kernel with 'make
> CC=your/fresh/gcc'.
> 
> And then change "cover": false in config to "cover": true.

Right, I'll see if I can pick the patch from there.