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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2013-09-10 08:26:09 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2013-09-25 06:49:46 -0700
commit64f26e5c86af9ce8615721340c8282f2b148c9aa (patch)
tree31bfe356b8a59dac492aa38f22b83fe20717bcb5 /Documentation/kernel-per-CPU-kthreads.txt
parent64d3b7a1d5289486df2d8bce36e23ed5ebc80a3d (diff)
downloadlinux-rt-64f26e5c86af9ce8615721340c8282f2b148c9aa.tar.gz
kthread: Add pointer to vmstat-avoidance patch
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'Documentation/kernel-per-CPU-kthreads.txt')
-rw-r--r--Documentation/kernel-per-CPU-kthreads.txt17
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.