linux-kernel - Re: [PATCH] perf record: mmap output file

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Tue, 15 Oct 2013 19:58:34 -0600
From:	David Ahern <dsahern@...il.com>
To:	Namhyung Kim <namhyung@...nel.org>
CC:	acme@...stprotocols.net, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Jiri Olsa <jolsa@...hat.com>, Mike Galbraith <efault@....de>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH] perf record: mmap output file - v2

On 10/15/13 7:52 PM, Namhyung Kim wrote:
> Aha, okay.  So it mostly matters to syscall tracing, right?  For a
> normal record session, it seems that the effect is not that large:

Yes, that's in the description "When recording raw_syscalls for the 
entire system"

There is a small benefit to all record sessions -- mmap+memcpy has less 
overhead than write(). I still need to look at Ingo's suggestion to use 
non-temporal stores which might reduce the overhead of the memcpy.

Try a workload that generates a HUGE data file -- say a full kernel 
build (e.g., perf record -g -- make O=/tmp/kbuild -j 16). You should see 
a much larger benefit from the mmap route. Be sure to use your callchain 
enhancements to look at that 1+G file. ;-)

David
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/