On Thu, Apr 23 2009, Christoph Hellwig wrote: > Stumbled over these gems recently when investigating the > lock_super/unlock_super removal. > > These were added in commit 22e2c507c301c3dbbcf91b4948b88f78842ee6c9 > > [PATCH] Update cfq io scheduler to time sliced design > > which unfortunately doesn't contain any comments about it. It seems to > be used to allow boosting priority for some sort of central fs metadata > updates, at least what the usage in the reiserfs journal code > looks like that. > > Do you happen to have some notes/anecdotes about it so that we can > document it, give it saner naming and use it directly in the > spots that need it (including inside xfs, btrfs, etc) instead of lock_super? The intent was to add some sort of notification mechanism from the file system to inform the IO scheduler (and others?) that this process is how holding a file system wide resource. So if you have a low priority process getting access to such a resource, you want to boost its priority to avoid higher priority apps getting stuck beind it. Sort of a poor mans priority inheritance. It would be wonderful if you could kick this process more into gear on the fs side... -- Jens Axboe -- 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
