Commit-ID: 64f26e5c86af9ce8615721340c8282f2b148c9aa Gitweb: http://git.kernel.org/tip/64f26e5c86af9ce8615721340c8282f2b148c9aa Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> AuthorDate: Tue, 10 Sep 2013 08:26:09 -0700 Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> CommitDate: Wed, 25 Sep 2013 06:49:46 -0700 kthread: Add pointer to vmstat-avoidance patch Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx> --- Documentation/kernel-per-CPU-kthreads.txt | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/Documentation/kernel-per-CPU-kthreads.txt b/Documentation/kernel-per-CPU-kthreads.txt index 32351bf..827104f 100644 --- a/Documentation/kernel-per-CPU-kthreads.txt +++ b/Documentation/kernel-per-CPU-kthreads.txt @@ -181,12 +181,17 @@ To reduce its OS jitter, do any of the following: make sure that this is safe on your particular system. d. It is not possible to entirely get rid of OS jitter from vmstat_update() on CONFIG_SMP=y systems, but you - can decrease its frequency by writing a large value to - /proc/sys/vm/stat_interval. The default value is HZ, - for an interval of one second. Of course, larger values - will make your virtual-memory statistics update more - slowly. Of course, you can also run your workload at - a real-time priority, thus preempting vmstat_update(). + can decrease its frequency by writing a large value + to /proc/sys/vm/stat_interval. The default value is + HZ, for an interval of one second. Of course, larger + values will make your virtual-memory statistics update + more slowly. Of course, you can also run your workload + at a real-time priority, thus preempting vmstat_update(), + but if your workload is CPU-bound, this is a bad idea. + However, there is an RFC patch from Christoph Lameter + (based on an earlier one from Gilad Ben-Yossef) that + reduces or even eliminates vmstat overhead for some + workloads at https://lkml.org/lkml/2013/9/4/379. e. If running on high-end powerpc servers, build with CONFIG_PPC_RTAS_DAEMON=n. This prevents the RTAS daemon from running on each CPU every second or so. -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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