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author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-01-24 22:24:14 -0800 |
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committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-02-26 11:57:28 -0800 |
commit | 89bf5d82ed451f02329bbbb06ac365e96b18804d (patch) | |
tree | da9009ae1bf0bdb761ac2265b992bdc9c124fec4 | |
parent | d2af1ad73e7a22ed3e04374896fee0eb300c05c3 (diff) | |
download | linux-89bf5d82ed451f02329bbbb06ac365e96b18804d.tar.bz2 |
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@linux.vnet.ibm.com>
-rw-r--r-- | Documentation/kernel-per-CPU-kthreads.txt | 18 |
1 files changed, 10 insertions, 8 deletions
diff --git a/Documentation/kernel-per-CPU-kthreads.txt b/Documentation/kernel-per-CPU-kthreads.txt index f3cd299fcc41..81fe051c4447 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 |