On Oct 28, 2008 16:16 -0400, Josef Bacik wrote: > I also have a min() check in there to make sure we don't sleep longer than > a jiffie in case our storage is super slow, this was requested by Andrew. Is there a particular reason why 1 jiffie is considered the "right amount" of time to sleep, given this is a kernel config parameter and has nothing to do with the storage? Considering a seek time in the range of ~10ms this would only be right for HZ=100 and the wait would otherwise be too short to maximize batching within a single transaction. > type threads with patch without patch > sata 2 24.6 26.3 > sata 4 49.2 48.1 > sata 8 70.1 67.0 > sata 16 104.0 94.1 > sata 32 153.6 142.7 In the previous patch where this wasn't limited it had better performance even for the 2 thread case. With the current 1-jiffie wait it likely isn't long enough to batch every pair of operations and every other operation waits an extra amount before giving up too soon. Previous patch: type threads patch unpatched sata 2 34.6 26.2 sata 4 58.0 48.0 sata 8 75.2 70.4 sata 16 101.1 89.6 I'd recommend changing the patch to have a maximum sleep time that has a fixed maximum number of milliseconds (15ms should be enough for even very old disks). That said, this would be a minor enhancement and should NOT be considered a reason to delay this patch's inclusion into -mm or the ext4 tree. PS - it should really go into jbd2 also Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc. -- 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
