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Date: Tue, 3 Mar 2015 08:37:38 -0800 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: linux-kernel@...r.kernel.org Cc: mingo@...nel.org, laijs@...fujitsu.com, dipankar@...ibm.com, akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com, josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com, dvhart@...ux.intel.com, fweisbec@...il.com, oleg@...hat.com, bobby.prani@...il.com, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> Subject: [PATCH tip/core/rcu 4/6] documentation: Update per-CPU kthreads documentation From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com> --- Documentation/kernel-per-CPU-kthreads.txt | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/Documentation/kernel-per-CPU-kthreads.txt b/Documentation/kernel-per-CPU-kthreads.txt index 81fe051c4447..f4cbfe0ba108 100644 --- a/Documentation/kernel-per-CPU-kthreads.txt +++ b/Documentation/kernel-per-CPU-kthreads.txt @@ -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. -- 1.8.1.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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