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

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Message-ID: <CACT4Y+bUG6+GEQzG3sR+3rvyZkg=E+85x1sMkQme3RuViBHXxQ@mail.gmail.com>
Date:	Mon, 15 Feb 2016 17:54:51 +0100
From:	Dmitry Vyukov <dvyukov@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
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 5:41 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Mon, Feb 15, 2016 at 05:35:51PM +0100, Dmitry Vyukov wrote:
>> > root@...-ep:~/gopath/src/github.com/google/syzkaller# bin/syz-manager -config perf.cfg -v 1 -debug
>> > 2016/02/15 17:12:50 bad config syzkaller param: can't find bin/syz-execprog
>> >
>> > And its right, no such thing as bin/syz-execprog
>>
>>
>> Please also do:
>>
>> $ make execprog
>>
>> And replace:
>>
>>         "nocover": true,
>>         "nodropprivs": true,
>>
>> in config file with:
>>
>>         "cover": false,
>>         "dropprivs": false,
>>
>> (that's changed since I wrote the instructions).
>
> 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.

> 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.

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.