linux-kernel - Re: [PATCH] perf record: Allow poll timeout to be specified

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

Date:	Wed, 25 Mar 2015 13:38:55 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	David Ahern <david.ahern@...cle.com>
Cc:	acme@...nel.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Jiri Olsa <jolsa@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Stephane Eranian <eranian@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH] perf record: Allow poll timeout to be specified

On Tue, Mar 24, 2015 at 12:09:48PM -0400, David Ahern wrote:
> Record currently wakes up based on watermarks to read events from the mmaps and
> write them out to the file. The result is a file that can have large blocks of
> events per mmap before a finished round event is added to the stream.  This in
> turn affects the quantity of events that have to be passed through the ordered
> events queue before results can be displayed to the user. For commands like
> perf-script this can lead to long unnecessarily long delays before a user gets
> output. Large systems (e.g, 1024 cpus) further compound this effect. I have seen
> instances where I have to wait 45 minutes for perf-script to process a 5GB file
> before any events are shown.

so you have pipe to perf script, right?

> 
> This patch adds an option to perf-record to allow a user to specify the
> poll timeout in msec. For example using 100 msec timeouts similar to perf-top
> means the mmaps are traversed much more frequently leading to a smoother
> analysis side.

there's also the '--no-buffering' option that sets:

                attr->watermark = 0;
                attr->wakeup_events = 1;

but that's just the other edge, which is not what you'd want

I think it's good to have user side configurable as well

Acked-by: Jiri Olsa <jolsa@...nel.org>

thanks,
jirka
--
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/