Commit-ID: 89bf5d82ed451f02329bbbb06ac365e96b18804d Gitweb: http://git.kernel.org/tip/89bf5d82ed451f02329bbbb06ac365e96b18804d Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> AuthorDate: Sat, 24 Jan 2015 22:24:14 -0800 Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> CommitDate: Thu, 26 Feb 2015 11:57:28 -0800 documentation: Update based on on-demand vmstat workers Now that the on-demand vmstat workers commit is in mainline, it is possible to eliminate vmstat_update()-induced OS jitter. This commit updates the documentation accordingly. Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> --- Documentation/kernel-per-CPU-kthreads.txt | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) diff --git a/Documentation/kernel-per-CPU-kthreads.txt b/Documentation/kernel-per-CPU-kthreads.txt index f3cd299..81fe051 100644 --- a/Documentation/kernel-per-CPU-kthreads.txt +++ b/Documentation/kernel-per-CPU-kthreads.txt @@ -190,14 +190,16 @@ To reduce its OS jitter, do any of the following: on each CPU, including cs_dbs_timer() and od_dbs_timer(). WARNING: Please check your CPU specifications to 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(), + d. As of v3.18, Christoph Lameter's on-demand vmstat workers + commit prevents OS jitter due to vmstat_update() on + CONFIG_SMP=y systems. Before v3.18, is not possible + to entirely get rid of the OS jitter, 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(), 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 -- 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
|