On Tue, 22 Apr 2008 10:51:25 -0400 Theodore Tso <tytso@xxxxxxx> wrote: > On Tue, Apr 22, 2008 at 09:18:47AM -0500, Jose R. Santos wrote: > > > @@ -1638,6 +1654,19 @@ static void PRS(int argc, char *argv[]) > > > > > > if (inode_size == 0) > > > inode_size = get_int_from_profile(fs_types, "inode_size", 0); > > > + if (!flex_bg_size && (fs_param.s_feature_incompat & > > > + EXT4_FEATURE_INCOMPAT_FLEX_BG)) > > > + get_int_from_profile(fs_types, "flex_bg_size", 8); > > > > A default of 256 block groups to pack seems a bit high base on some of > > the performance testing that I've done. At some point having the inodes > > too far away from the data blocks begins to affect performance > > (especially on read operations). The optimum number of groups depends > > a lot on platter density of the hard drive so I expect that we can > > increase the default grouping size as time goes by. Using 128 groups > > as already showing performance degradation on read operations on some > > of my smaller disks (147GB). For now, I would change this to 6 (64 > > groups) as this is a good balance for both big an small disks. > > Actually this is 8 (as in 2**3), which was intentionally very small, > because I was being conservative. I could change it to be 64 if you > think it is a better balance. As you can see, it gets set later on > down here. I see that now, guess I should not read code with out having breakfast. I think 8 is a very safe and conservative number, maybe to conservative. The 64 group packing was the number I found to be a overall improvement with the limited number of drives that I had to test with. Haven't done any testing on old drives or laptop drive with slow spindle speed but I would think 16 or 32 would be safe here unless the drive is really old and small. > > > > + fs_param.s_log_groups_per_flex = int_log2(flex_bg_size); > > And, in fact the biggest bug which both you and I missed was that this: > > > > + get_int_from_profile(fs_types, "flex_bg_size", 8); > > Should have been this: > > flex_bg_size = get_int_from_profile(fs_types, "flex_bg_size", 8); > > <Dons paper bag> > > - Ted -JRS -- 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
