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| -rw-r--r-- | Documentation/kernel-per-CPU-kthreads.txt | 17 |
1 files changed, 11 insertions, 6 deletions
diff --git a/Documentation/kernel-per-CPU-kthreads.txt b/Documentation/kernel-per-CPU-kthreads.txt index 32351bfabf20..827104fb9364 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. |