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[PATCH] rcu batch tuning

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This patch adds new tunables for RCU queue and finished batches.  There are
two types of controls - number of completed RCU updates invoked in a batch
(blimit) and monitoring for high rate of incoming RCUs on a cpu (qhimark,
qlowmark).

By default, the per-cpu batch limit is set to a small value.  If the input
RCU rate exceeds the high watermark, we do two things - force quiescent
state on all cpus and set the batch limit of the CPU to INTMAX.  Setting
batch limit to INTMAX forces all finished RCUs to be processed in one shot.
 If we have more than INTMAX RCUs queued up, then we have bigger problems
anyway.  Once the incoming queued RCUs fall below the low watermark, the
batch limit is set to the default.

Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Dipankar Sarma
2006-03-07 21:55:33 -08:00
committed by Linus Torvalds
parent e2bab3d924
commit 21a1ea9eb4
3 changed files with 76 additions and 19 deletions
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13
Documentation/kernel-parameters.txt
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@@ -1284,6 +1284,19 @@ running once the system is up.
New name for the ramdisk parameter.
See Documentation/ramdisk.txt.
rcu.blimit= [KNL,BOOT] Set maximum number of finished
RCU callbacks to process in one batch.
rcu.qhimark= [KNL,BOOT] Set threshold of queued
RCU callbacks over which batch limiting is disabled.
rcu.qlowmark= [KNL,BOOT] Set threshold of queued
RCU callbacks below which batch limiting is re-enabled.
rcu.rsinterval= [KNL,BOOT,SMP] Set the number of additional
RCU callbacks to queued before forcing reschedule
on all cpus.
rdinit= [KNL]
Format: <full_path>
Run specified binary instead of /init from the ramdisk,