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Message-ID: <4BE417CB.7000806@cfl.rr.com> Date: Fri, 7 May 2010 09:38:19 -0400 From: Phillip Susi <psusi@....rr.com> To: linux-fsdevel@...r.kernel.org, Linux-kernel <linux-kernel@...r.kernel.org> Subject: unified page and buffer cache? (was: readahead on directories) I thought that the buffer and page caches were unified long ago, but last night I modified ureadahead to call readahead() directly on the block device for all physical extents involved rather than open() each file and readahead() on that. It read all of the related blocks into the buffer cache nice and fast, which was then ignored and the data was read again when accessed normally during boot. So it seems that the buffer cache and page cache are still separate, and normal files only use the page cache, and directories only use the buffer cache, which is why readahead() fails when called on a directory. Can anyone confirm that my disappointed understanding is correct? I started experimenting with a workaround where I readahead directories via the block device, and normal files the normal way. This seems to do the trick, but is sub optimal since you have to read in two passes, picking up the directories on the first pass, then going back for the files. -- 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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