From: "Darrick J. Wong" Subject: [PATCH v5 0/4] crc32c: Add faster algorithm and self-test code Date: Tue, 04 Oct 2011 16:53:57 -0700 Message-ID: <20111004235357.1560.12602.stgit@elm3c44.beaverton.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: Joakim Tjernlund , Bob Pearson , linux-kernel , Mingming Cao , linux-crypto , linux-fsdevel , linux-ext4@vger.kernel.org To: Andreas Dilger , Herbert Xu , Theodore Tso , David Miller , "Darrick J. Wong" Return-path: Sender: linux-crypto-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Hi all, This patchset (re)uses Bob Pearson's crc32 slice-by-8 code to stamp out a software crc32c implementation. It requires that all ten of his patches (at least the ones dated 31 Aug 2011) be applied. It removes the crc32c implementation in crypto/ in favor of using the stamped-out one in lib/. There is also a change to Kconfig so that the kernel builder can pick an implementation best suited for the hardware. The motivation for this patchset is that I am working on adding full metadata checksumming to ext4. 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. 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. --D