linux-kernel - Re: [PATCH 0/7] writeback: avoid touching dirtied

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Message-ID: <20111022065926.GA31074@localhost>
Date:	Sat, 22 Oct 2011 14:59:26 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Jan Kara <jack@...e.cz>
Cc:	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	Dave Chinner <david@...morbit.com>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Tang, Feng" <feng.tang@...el.com>
Subject: Re: [PATCH 0/7] writeback: avoid touching dirtied_when on blocked
 inodes

> In general it looks better we first root case the "decreasing wrote
> pages by writeback_single_inode() over time" problem before looking
> into further steps..

The problem shows up in many of the regression cases. For example,
the thresh=1G/ext4-100dd case with patches 1-4 applied will not only
see nr_writeback occasionally dropped low (bdi_dirty_state-8:0.png),
but also see repeated pattern of nr_wrote by writeback_single_inode()
slowly decreasing to 0 during some period of dozens of seconds
(writeback_single_inode.png).

Thanks,
Fengguang

Download attachment "bdi_dirty_state-8:0.png" of type "image/png" (42728 bytes)

Download attachment "balance_dirty_pages-pages.png" of type "image/png" (85151 bytes)

Download attachment "writeback_single_inode.png" of type "image/png" (52548 bytes)

Download attachment "iostat-misc.png" of type "image/png" (102612 bytes)