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Date: Fri, 7 May 2010 20:46:17 -0400 From: tytso@....edu To: Phillip Susi <psusi@....rr.com> Cc: Matthew Wilcox <matthew@....cx>, linux-fsdevel@...r.kernel.org, Linux-kernel <linux-kernel@...r.kernel.org> Subject: Re: unified page and buffer cache? On Fri, May 07, 2010 at 11:45:34AM -0400, Phillip Susi wrote: > > Back to the drawing board I guess. Maybe ext could be fixed to use an > inode mapping for directories instead of relying on the block device > mapping, then I could readahead() the directory instead of having to go > to the block device at all. Ext2 does use the page cache for directories. Ext3 and Ext4 access directories via buffer heads because of the journaling requirement. In *theory* they could be modified to use the page cache, given that we can do data journaling for files, and files live in the page cache --- however, for cases where the PAGE_SIZE > FS_BLOCKSIZE, which will happen if you are using 1k or 2k block filesystems, or on the Power Architecture or on the Itanic where the page size is 16k, updates to the directory will be much less efficient, since we journal changes to data files on page granularity and not buffer granuality. Furthermore, someone would have to supply me with the patches; it's pretty low on my priority list. And people on the Power and ia64 platforms won't be happy.... - Ted -- 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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