On Fri, 24 Aug 2007 21:24:58 +0800 Fengguang Wu <wfg@xxxxxxxxxxxxxxxx> wrote: > > 2) s_dirty and s_io both become radix trees. s_dirty is indexed by > > a sequence number that corresponds to age. It is treated as a big > > circular indexed list that can wrap around over time. Radix tree > > tags are used both on s_dirty and s_io to flag which inodes are in > > progress. > > It's meaningless to convert s_io to radix tree. Because inodes on s_io > will normally be sent to block layer elevators at the same time. Not entirely, using a radix tree instead lets you tag things instead of doing the current backflips across three lists. > > Also s_dirty holds 30 seconds of inodes, while s_io only 5 seconds. > The more inodes, the more chances of good clustering. That's the > general rule. > > s_dirty is the right place to do address-clustering. > As for the dirty_expire_interval parameter on dirty age, > we can apply a simple rule: do one full scan/sweep over the > fs-address-space in every 30s, syncing all inodes encountered, > and sparing those newly dirtied in less than 5s. With that rule, > any inode will get synced after being dirtied for 5-35 seconds. This gives you an O(inodes dirty) behavior instead of the current O(old inodes). It might not matter, but walking the radix tree is more expensive than walking a list. But, I look forward to your patches, we can tune from there. -chris - 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
