linux-kernel - Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1)

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:	Mon, 14 Dec 2015 17:56:14 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Ingo Molnar <mingo@...nel.org>, David Ahern <dsahern@...il.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Jiri Olsa <jolsa@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	Stephane Eranian <eranian@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1)

On Tue, Dec 15, 2015 at 01:38:30AM +0900, Namhyung Kim wrote:
> It requires many changes, but basically I also like the split-up since
> it's easier to deal with.  IIRC there was an opinion (Andi?) regarding
> single-file vs multi-file.  The file access will be better for single
> file so I changed my earlier implementation to use indexed single data
> file instead of multiple files.

The page-cache has a lock per inode, so by having all CPUs populate the
one file you get contention on that.

Also, I suppose you'll have to arbitrate ranges in that file for each
cpu to make it work, that too could get you some contention.

Having a file per cpu avoids all that.
--
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/