On Tue, Sep 27, 2011 at 03:12:39PM -0700, Darrick J. Wong wrote: > Hi all, > > This patchset replaces the current crc32c software implementation, which uses a > slow per-byte lookup table algorithm, with a faster implementation that uses an > adaptation of the slice-by-8 algorithm that Bob Pearson has been pushing for > crc32. > > The motivation for this patchset is that I am working on adding full metadata > checksumming to ext4[1]. As far as performance impact of adding checksumming > goes, I see nearly no change with a standard mail server ffsb simulation. On a > test that involves only file creation and deletion and extent tree writes, I > see a drop of about 50 pcercent with the current kernel crc32c implementation; > this improves to a drop of about 20 percent with the enclosed crc32c code. > > When metadata is usually a small fraction of total IO, this new implementation > doesn't help much because metadata is usually a small fraction of total IO. > However, when we are doing IO that is almost all metadata (such as rm -rf'ing a > tree), then this patch speeds up the operation substantially. > > Please have a look at the patches, and please feel free to suggest any changes. > I will be at LPC next week if anyone wishes to discuss, debate, or protest. Oops, ignore that sentence, since LPC has long passed. :( --D > > Incidentally, given that iscsi, sctp, and btrfs also use crc32c, this patchset > should improve their speed as well. I have not yet quantified that, however. > > v2: Use the crypto test manager code to check crc32c operation. > > --D > > [1] https://ext4.wiki.kernel.org/index.php/Ext4_Metadata_Checksums -- 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
