On Thu, Apr 20, 2017 at 12:52:55PM -0700, Liu Bo wrote: > On Thu, Apr 20, 2017 at 10:09:39AM +0800, Qu Wenruo wrote: > > > > > > At 04/20/2017 09:58 AM, Liu Bo wrote: > > > On Thu, Apr 20, 2017 at 09:52:00AM +0800, Qu Wenruo wrote: > > > > > > > > > [...] > > > > > > > > > > If I understand it correctly, what it's missing currently is 'merge', > > > > > a > > > > > straightfoward idea is to make use of the 'merge' ability of > > > > > btrfs_get_extent. > > > > > > Since btrfs_get_extent_fiemap is a wrapper of btrfs_get_extent, does > > > > > it make > > > > > sense if we make btrfs_get_extent_fiemap iterate all extent maps > > > > > within the > > > > > range passing to it or just one more extent map to check if > > > > > btrfs_get_extent > > > > > could return a merged extent map before returning? > > > > > > > > So your idea to to do the merging inside btrfs_get_extent(), instead of > > > > merging it in extent_fiemap()? > > > > > > > > > > No, merge ems inside the wrapper, ie. btrfs_get_extent_fiemap(). > > > > Then llseek() with SEEK_HOLE/SEEK_DATA also get affected. > > > > So limiting the extra time to merging extent maps in fiemap is still valid. > > > > Per my test, the v3 patch doesn't make big difference on the side of > performance.
I think the point was not to improve performance, but to make the fiemap output correct. But anyway it's good that the performance does not degrade. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
