linux-kernel - Re: [RFC PATCH 0/5] Support multiple pages allocation

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]

Message-ID: <20130710003142.GA2152@lge.com>
Date:	Wed, 10 Jul 2013 09:31:42 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	Zhang Yanfei <zhangyanfei.yes@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Glauber Costa <glommer@...il.com>,
	Johannes Weiner <hannes@...xchg.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>,
	Hugh Dickins <hughd@...gle.com>,
	Minchan Kim <minchan@...nel.org>,
	Jiang Liu <jiang.liu@...wei.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/5] Support multiple pages allocation

On Thu, Jul 04, 2013 at 12:00:44PM +0200, Michal Hocko wrote:
> On Thu 04-07-13 13:24:50, Joonsoo Kim wrote:
> > On Thu, Jul 04, 2013 at 12:01:43AM +0800, Zhang Yanfei wrote:
> > > On 07/03/2013 11:51 PM, Zhang Yanfei wrote:
> > > > On 07/03/2013 11:28 PM, Michal Hocko wrote:
> > > >> On Wed 03-07-13 17:34:15, Joonsoo Kim wrote:
> > > >> [...]
> > > >>> For one page allocation at once, this patchset makes allocator slower than
> > > >>> before (-5%). 
> > > >>
> > > >> Slowing down the most used path is a no-go. Where does this slow down
> > > >> come from?
> > > > 
> > > > I guess, it might be: for one page allocation at once, comparing to the original
> > > > code, this patch adds two parameters nr_pages and pages and will do extra checks
> > > > for the parameter nr_pages in the allocation path.
> > > > 
> > > 
> > > If so, adding a separate path for the multiple allocations seems better.
> > 
> > Hello, all.
> > 
> > I modify the code for optimizing one page allocation via likely macro.
> > I attach a new one at the end of this mail.
> > 
> > In this case, performance degradation for one page allocation at once is -2.5%.
> > I guess, remained overhead comes from two added parameters.
> > Is it unreasonable cost to support this new feature?
> 
> Which benchmark you are using for this testing?

I use my own module which do allocation repeatedly.

> 
> > I think that readahead path is one of the most used path, so this penalty looks
> > endurable. And after supporting this feature, we can find more use cases.
> 
> What about page faults? I would oppose that page faults are _much_ more
> frequent than read ahead so you really cannot slow them down.

You mean page faults for anon?
Yes. I also think that it is much more frequent than read ahead.
Before futher discussion, I will try to add a separate path
for the multiple allocations.

Thanks.

> 
> [...]
> -- 
> Michal Hocko
> SUSE Labs
> 
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@...ck.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a>
--
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/