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Date: Mon, 26 Jul 2010 20:56:35 +0800 From: Wu Fengguang <fengguang.wu@...el.com> To: Mel Gorman <mel@....ul.ie> Cc: Andrew Morton <akpm@...ux-foundation.org>, Dave Chinner <david@...morbit.com>, Jan Kara <jack@...e.cz>, Christoph Hellwig <hch@...radead.org>, Chris Mason <chris.mason@...cle.com>, Jens Axboe <jens.axboe@...cle.com>, LKML <linux-kernel@...r.kernel.org>, "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>, "linux-mm@...ck.org" <linux-mm@...ck.org> Subject: Re: [PATCH 4/6] writeback: sync expired inodes first in background writeback > > @@ -232,8 +232,15 @@ static void move_expired_inodes(struct l > > while (!list_empty(delaying_queue)) { > > inode = list_entry(delaying_queue->prev, struct inode, i_list); > > if (expire_interval && > > - inode_dirtied_after(inode, older_than_this)) > > - break; > > + inode_dirtied_after(inode, older_than_this)) { > > + if (wbc->for_background && > > + list_empty(dispatch_queue) && list_empty(&tmp)) { > > + expire_interval >>= 1; > > + older_than_this = jiffies - expire_interval; > > + continue; > > + } else > > + break; > > + } > > This needs a comment. > > I think what it is saying is that if background flush is active but no > inodes are old enough, consider newer inodes. This is on the assumption > that page reclaim has encountered dirty pages and the dirty inodes are > still too young. Yes this should be commented. How about this one? @@ -232,8 +232,20 @@ static void move_expired_inodes(struct l while (!list_empty(delaying_queue)) { inode = list_entry(delaying_queue->prev, struct inode, i_list); if (expire_interval && - inode_dirtied_after(inode, older_than_this)) + inode_dirtied_after(inode, older_than_this)) { + /* + * background writeback will start with expired inodes, + * and then fresh inodes. This order helps reducing + * the number of dirty pages reaching the end of LRU + * lists and cause trouble to the page reclaim. + */ + if (wbc->for_background && + list_empty(dispatch_queue) && list_empty(&tmp)) { + expire_interval = 0; + continue; + } break; + } if (sb && sb != inode->i_sb) do_sb_sort = 1; sb = inode->i_sb; 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/
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