On 08/03/2010 05:44 PM, Andreas Dilger wrote: > On 2010-08-03, at 16:30, Eric Sandeen wrote: >> commit 3d0518f4758eca4339e75e5b9dbb7e06a5ce08b4 Author: Wei Yongjun >> <yjwei@xxxxxxxxxxxxxx> Date: Sat Feb 14 23:01:36 2009 -0500 >> >> ext4: New rec_len encoding for very large blocksizes >> >> The rec_len field in the directory entry is 16 bits, so to encode >> blocksizes larger than 64k becomes problematic. This patch allows >> us to supprot block sizes up to 256k, by using the low 2 bits to >> extend the range of rec_len to 2**18-1 (since valid rec_len sizes >> must be a multiple of 4). We use the convention that a rec_len of >> 0 or 65535 means the filesystem block size, for compatibility with >> older kernels. >> >> It's a novel solution to the problem, but I'm not sure it's a >> problem that needs to be solved today since we cannot even make >> filesystems with >>> >>> 64k blocks: > > I don't object to reverting the > 64kB support, but we should strive > to keep 64kB directory blocks working, if that is possibly going to > break with reverting this patch. I don't think any of the other extN > code is expecting to handle block sizes larger than 64kB, so little > value to do it just in the directory handling code. As far as I know, reverting it won't break 64kb dir blocks...? A simpler solution to the perf problem might be to just re-inline the function, but I'm not sure what the point of all this is, as you say. Thanks, -Eric >> Just for reference, the testing I did on RHEL6 was: >> >> # bonnie++ -u root -s 0 -f -x 200 -d /mnt/test -n 32 >> >> (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... > > Nothing to sneeze at. > > 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
