linux-kernel - Re: [PATCH 1/1] mm: vmstat: introducing vm counter for slowpath

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: <20150807074422.GE26566@dhcp22.suse.cz>
Date:	Fri, 7 Aug 2015 09:44:22 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Pintu Kumar <pintu.k@...sung.com>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, minchan@...nel.org, dave@...olabs.net,
	koct9i@...il.com, mgorman@...e.de, vbabka@...e.cz,
	js1304@...il.com, hannes@...xchg.org, alexander.h.duyck@...hat.com,
	sasha.levin@...cle.com, cl@...ux.com, fengguang.wu@...el.com,
	cpgs@...sung.com, pintu_agarwal@...oo.com, pintu.k@...look.com,
	vishnu.ps@...sung.com, rohit.kr@...sung.com
Subject: Re: [PATCH 1/1] mm: vmstat: introducing vm counter for slowpath

On Fri 07-08-15 12:38:54, Pintu Kumar wrote:
> This patch add new counter slowpath_entered in /proc/vmstat to
> track how many times the system entered into slowpath after
> first allocation attempt is failed.

This is too lowlevel to be exported in the regular user visible
interface IMO.

> This is useful to know the rate of allocation success within
> the slowpath.

What would be that information good for? Is a regular administrator
expected to consume this value or this is aimed more to kernel
developers? If the later then I think a trace point sounds like a better
interface.

> This patch is tested on ARM with 512MB RAM.
> A sample output is shown below after successful boot-up:
> shell> cat /proc/vmstat
> nr_free_pages 4712
> pgalloc_normal 1319432
> pgalloc_movable 0
> pageoutrun 379
> allocstall 0
> slowpath_entered 585
> compact_stall 0
> compact_fail 0
> compact_success 0
> 
> >From the above output we can see that the system entered
> slowpath 585 times.
> But the existing counter kswapd(pageoutrun), direct_reclaim(allocstall),
> direct_compact(compact_stall) does not tell this value.
> >From the above value, it clearly indicates that the system have
> entered slowpath 585 times. Out of which 379 times allocation passed
> through kswapd, without performing direct reclaim/compaction.
> That means the remaining 206 times the allocation would have succeeded
> using the alloc_pages_high_priority.
> 
> Signed-off-by: Pintu Kumar <pintu.k@...sung.com>
-- 
Michal Hocko
SUSE Labs
--
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/