-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 06/23/2014 03:16 PM, Tim Chen wrote: > Thanks to the review from Jason, Andi and Peter. I've updated the > code as Peter suggested with simplified logic. > > When a system is lightly loaded (i.e. no more than 1 job per cpu), > attempt to pull job to a cpu before putting it to idle is > unnecessary and can be skipped. This patch adds an indicator so > the scheduler can know when there's no more than 1 active job is on > any CPU in the system to skip needless job pulls. > > On a 4 socket machine with a request/response kind of workload > from clients, we saw about 0.13 msec delay when we go through a > full load balance to try pull job from all the other cpus. While > 0.1 msec was spent on processing the request and generating a > response, the 0.13 msec load balance overhead was actually more > than the actual work being done. This overhead can be skipped much > of the time for lightly loaded systems. > > With this patch, we tested with a netperf request/response workload > that has the server busy with half the cpus in a 4 socket system. > We found the patch eliminated 75% of the load balance attempts > before idling a cpu. > > The overhead of setting/clearing the indicator is low as we already > gather the necessary info while we call add_nr_running and > update_sd_lb_stats. We switch to full load balance load immediately > if any cpu got more than one job on its run queue in > add_nr_running. We'll clear the indicator to avoid load balance > when we detect no cpu's have more than one job when we scan the > work queues in update_sg_lb_stats. We are aggressive in turning on > the load balance and opportunistic in skipping the load balance. > > Signed-off-by: Tim Chen <[email protected]> Acked-by: > Jason Low <[email protected]>
Acked-by: Rik van Riel <[email protected]> - -- All rights reversed -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBAgAGBQJTqH50AAoJEM553pKExN6DYj4H/17YlyWg0QDoNrkNbhEi8SfD I0BsklbbDIpcq9hKpwiJOCiQNeVLjMwhTniKOOXj1LgbtSsHYz7Scac/vt9sJRsy PLJKoQt43lSv7Ff3mJFbUZG5u2RWoLs8TLuSFhPd39J8XupJX9jVe3GejBsp8lN4 Mpmo2DD6FvjvF2mpIP+CpEDFQZNeEZBb9UMvAJCjAU4JwdodwFkLRgxTWyOUSFpS eOhDj99nRgyCz0LwLaVD2mfi29B/C5giIk70G+1II9BjTDGlFJC9X5FairZ3bM+K 6//BDq1baNnVu7pKKtQe8bLhNFQ1z1WNtgDr8L9c6dw9rLI+5AGjZb+KK5mMnG8= =goKD -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
