Commit f1360570 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

documentation: Update per-CPU kthreads documentation 



Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent c2519784

Documentation/kernel-per-CPU-kthreads.txt

+11 −5
Original line number Diff line number Diff line
@@ -205,7 +205,9 @@ To reduce its OS jitter, do any of the following: 
		(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

	e.	Boot with "elevator=noop" to avoid workqueue use by

		the block layer.

	f.	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.

		(This will require editing Kconfig files and will defeat
@@ -213,12 +215,12 @@ To reduce its OS jitter, do any of the following: 
		due to the rtas_event_scan() function.

		WARNING:  Please check your CPU specifications to

		make sure that this is safe on your particular system.

	f.	If running on Cell Processor, build your kernel with

	g.	If running on Cell Processor, build your kernel with

		CBE_CPUFREQ_SPU_GOVERNOR=n to avoid OS jitter from

		spu_gov_work().

		WARNING:  Please check your CPU specifications to

		make sure that this is safe on your particular system.

	g.	If running on PowerMAC, build your kernel with

	h.	If running on PowerMAC, build your kernel with

		CONFIG_PMAC_RACKMETER=n to disable the CPU-meter,

		avoiding OS jitter from rackmeter_do_timer().
@@ -260,8 +262,12 @@ Purpose: Detect software lockups on each CPU. 
To reduce its OS jitter, do at least one of the following:

1.	Build with CONFIG_LOCKUP_DETECTOR=n, which will prevent these

	kthreads from being created in the first place.

2.	Echo a zero to /proc/sys/kernel/watchdog to disable the

2.	Boot with "nosoftlockup=0", which will also prevent these kthreads

	from being created.  Other related watchdog and softlockup boot

	parameters may be found in Documentation/kernel-parameters.txt

	and Documentation/watchdog/watchdog-parameters.txt.

3.	Echo a zero to /proc/sys/kernel/watchdog to disable the

	watchdog timer.

3.	Echo a large number of /proc/sys/kernel/watchdog_thresh in

4.	Echo a large number of /proc/sys/kernel/watchdog_thresh in

	order to reduce the frequency of OS jitter due to the watchdog

	timer down to a level that is acceptable for your workload.