On 12/7/10 3:07 PM, Andrew Morton wrote: > On Tue, 07 Dec 2010 11:51:05 -0600 > Eric Sandeen <sandeen@xxxxxxxxxx> wrote: > >> The addition of 64k block capability in the rec_len_from_disk >> and rec_len_to_disk functions added a bit of math overhead which >> slows down file create workloads needlessly when the architecture >> cannot even support 64k blocks, thanks to page size limits. >> >> The directory entry checking can also be optimized a bit >> by sprinkling in some unlikely() conditions to move the >> error handling out of line. >> >> bonnie++ sequential file creates on a 512MB ramdisk speeds up >> from about 2200/s to about 2500/s, about a 14% improvement. >> > > hrm, that's an improbably-large sounding improvement from eliminating > just a few test-n-branches from a pretty heavyweight operation. And yet ... Yeah, I dunno. Part of it is that ext2_add_link does a linear search, so when you do rec_len_from_disk 50,000 times on a dir, that little bit adds up quite badly I suppose. Retesting at a bunch of different number-of-files in bonnie (with a small sample size so probably a little noise) |files per sec| files stock patched delta 10,000 12300 14700 +19% 20,000 6300 7600 +20% 30,000 4200 5000 +20% 40,000 3150 3700 +17% 50,000 2500 3000 +20% (again all on a 512MB ramdisk) *shrug* I'll believe my lyin' eyes, I guess. :) -Eric -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
