linux-kernel - Re: [PATCH] mm: cache largest vma

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, 11 Nov 2013 22:09:24 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Davidlohr Bueso <davidlohr@...com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Michel Lespinasse <walken@...gle.com>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Guan Xuetao <gxt@...c.pku.edu.cn>,
	"Chandramouleeswaran, Aswin" <aswin@...com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Frédéric Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH] mm: cache largest vma


* Davidlohr Bueso <davidlohr@...com> wrote:

> > Or is access to varied in the Oracle case that it's missing the cache 
> > all the time, because the rbtree causes many cachemisses as the 
> > separate nodes are accessed during an rb-walk?
> 
> Similar to get_cycles(), is there anyway to quickly measure the amount 
> of executed instructions? Getting the IPC for the mmap_cache (this of 
> course is constant) and the treewalk could give us a nice overview of 
> the function's cost. I was thinking of stealing some perf-stat 
> functionality for this but didn't get around to it. Hopefully there's an 
> easier way...

There's no such easy method I'm afraid (Frederic's probe based trigger 
facility will give us that and more - but it's not ready yet) - but you 
could try profiling the workload for significant cache-misses:

  perf record -e cache-misses ...

I _think_ if it's really catastrophic cache-misses then the rbtree walk 
should light up on the perf radar like crazy.

Thanks,

	Ingo
--
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/