On 2010-08-03, at 17:12, Ted Ts'o wrote: > On Tue, Aug 03, 2010 at 05:49:22PM -0500, Eric Sandeen wrote: >> As far as I know, reverting it won't break 64kb dir blocks...? > > I seem to recall there was some confusion about what was the correct > way of recording a rec_len of 64k --- 0 or 65535. So after reverting > the patch, we need to make sure we didn't end up breaking > compatibility with (a) existing file systems and (b) what older > versions of mke2fs may have generated. Right - the newer code accepts both EXT4_MAX_REC_LEN and 0 to mean "blocksize". The old code took EXT4_MAX_REC_LEN to mean "1 << 16". For filesystems with blocksize < 64k there is no difference, but I think it makes sense to continue to accept both EXT4_MAX_REC_LEN and "0". >>>> (this does 200 iterations) and got this for the file creations: >>>> >>>> ext4 stock: Average = 21206.8 files/s >>>> ext4 patched: Average = 22822.1 files/s >>>> >>>> This is a 7.6% improvement... > > So one way of dealing wih this is making it an inline, and then > #ifdef'ing out the more complex code if the page size is < 64k.... Should it also be put under "unlikely()", or for that matter, the whole thing could be #ifdef'd out for PAGE_SIZE < 65536 since we won't magically grow blocksize > PAGE_SIZE support without knowing it. Cheers, Andreas -- 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
