linux-kernel - Re: [PATCH 3/8] writeback: switch to per-bdi threads for flushing data

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Message-Id: <1252417606.14793.3.camel@desktop>
Date:	Tue, 08 Sep 2009 06:46:46 -0700
From:	Daniel Walker <dwalker@...o99.com>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	chris.mason@...cle.com, david@...morbit.com, hch@...radead.org,
	akpm@...ux-foundation.org, jack@...e.cz
Subject: Re: [PATCH 3/8] writeback: switch to per-bdi threads for flushing
 data

On Tue, 2009-09-08 at 11:23 +0200, Jens Axboe wrote:
> This gets rid of pdflush for bdi writeout and kupdated style cleaning.
> pdflush writeout suffers from lack of locality and also requires more
> threads to handle the same workload, since it has to work in a
> non-blocking fashion against each queue. This also introduces lumpy
> behaviour and potential request starvation, since pdflush can be starved
> for queue access if others are accessing it. A sample ffsb workload that
> does random writes to files is about 8% faster here on a simple SATA drive
> during the benchmark phase. File layout also seems a LOT more smooth in
> vmstat:


This patch has a checkpatch error, and couple of warnings.. Here's one
of the warnings which I though was concerning..

WARNING: trailing semicolon indicates no statements, indent implies
otherwise
#388: FILE: fs/fs-writeback.c:177:
+               } else if (wb->task);
+                       wake_up_process(wb->task);

I suppose that could be a defect .. btw, patch 7 of 8 also has a few
trivial warnings.

Daniel

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