linux-kernel - Re: [PATCH 0/5] [RFC] transfer ASYNC vmscan writeback IO to the flusher threads

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:	Fri, 30 Jul 2010 13:34:06 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Jan Kara <jack@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Dave Chinner <david@...morbit.com>,
	Chris Mason <chris.mason@...cle.com>,
	Nick Piggin <npiggin@...e.de>, Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Christoph Hellwig <hch@...radead.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Mel Gorman <mel@....ul.ie>, Minchan Kim <minchan.kim@...il.com>
Subject: Re: [PATCH 0/5]  [RFC] transfer ASYNC vmscan writeback IO to the
 flusher threads

On Fri, Jul 30, 2010 at 12:09:47AM +0800, Jan Kara wrote:
> On Thu 29-07-10 19:51:42, Wu Fengguang wrote:
> > Andrew,
> > 
> > It's possible to transfer ASYNC vmscan writeback IOs to the flusher threads.
> > This simple patchset shows the basic idea. Since it's a big behavior change,
> > there are inevitably lots of details to sort out. I don't know where it will
> > go after tests and discussions, so the patches are intentionally kept simple.
> > 
> > sync livelock avoidance (need more to be complete, but this is minimal required for the last two patches)
> > 	[PATCH 1/5] writeback: introduce wbc.for_sync to cover the two sync stages
> > 	[PATCH 2/5] writeback: stop periodic/background work on seeing sync works
> > 	[PATCH 3/5] writeback: prevent sync livelock with the sync_after timestamp
>   Well, essentially any WB_SYNC_NONE writeback is still livelockable if you
> just grow a file constantly. So your changes are a step in the right
> direction but won't fix the issue completely.

Right. We have complementary patches to prevent livelocks both inside
file and among files.

> But what we could do to fix
> the issue completely would be to just set wbc->nr_to_write to LONG_MAX
> before writing inode for sync use my livelock avoidance using page-tagging
> for this case (it wouldn't have the possible performance issue because we
> are going to write all the inode anyway).

Yeah your patches are good to avoid livelocking in one single busy file.
I didn't forgot them :)

>   I can write the patch but frankly there are so many patches floating
> around that I'm not sure what I should base it on...

Me confused too. It may take some time to quiet down..

Thanks,
Fengguang
--
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/