From mboxrd@z Thu Jan 1 00:00:00 1970 From: P@draigBrady.com Subject: gettimeofday scalability Date: Tue, 05 Oct 2004 17:36:06 +0100 Sender: netdev-bounce@oss.sgi.com Message-ID: <4162CD76.4070204@draigBrady.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable Cc: Ingo Molnar , Andrea Arcangeli Return-path: To: netdev@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org I'm starting to look again at the performance of my packet sniffer. Any performace tips are appreciated (I'm using irq affinity and CONFIG_PACKET_MMAP on 2.4.20 on a dual P4 xeon at present). In particular I was wondering about reducing the overhead of calling do_gettimeofday. I noticed in the following paper that the xeon is much less efficient than the P3 for gettimeofday (for the syscall at least): http://www.labs.fujitsu.com/en/techinfo/linux/lse-0211/lse-0211.pdf I've seen various gettimeofday locking speedup patches floating around for 2.4. There is a version from Stephen and Andrea that uses frlock, claiming 18%, and one from ingo that uses brlock. 2.6.8.1 uses seqlock, which contains the comment that it's not as cache friendly as brlock. So can anyone summarise the relative merits of these locking mechanisms, before I start benchmarking? thanks, P=C3=A1draig.