On Wed, Jul 28, 2010 at 10:28:55AM +0100, Steven Whitehouse wrote: > The META tag is used in GFS2 for tagging all metadata whether to the > journal or otherwise. Is there some reason why this isn't correct? My > understanding was that it was more or less an informational hint to > those watching blktrace, Unfortunately the META flag is overloaded in the CFQ I/O scheduler. It gives META requests a boost over other, including synchronous request. From all I could gather so far it's intended to give desktops better interactivity by boosting some metadata reads, while it should in that form never be used for writes. So far I failed badly in getting a clarification of which read requests need to be tagged and if we should not apply this boost to write request marked META so that they can be used for blktrace tagging. Unless we really want to boost all reads separating the META from the BOOST flag might be a good option, but I really need to understand better how it's supposed to use. Except for gfs2 big hammer tagging it's used in ext3/ext4 for all reads on directories, the quota file and for reading the actual inode structure. It's not used for indirect blocks, symlinks, the superblock and allocation bitmaps. XFS appears to set the META flag for both reads and writes, but that code is unreachable currently. I haven't removed it yet as I'm still wondering if it could be used correctly instead. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
