Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1558898

[PATCH tip/core/rcu 16/20] rcu: Enable RCU tracepoints by default to aid in debugging

Show all headers | View raw

From: Matt Fleming <matt@codeblueprint.co.uk>

While debugging a performance issue I needed to understand why
RCU sofitrqs were firing so frequently.

Unfortunately, the RCU callback tracepoints are hidden behind
CONFIG_RCU_TRACE which defaults to off in the upstream kernel and is
likely to also be disabled in enterprise distribution configs.

Enable it by default for CONFIG_TREE_RCU. However, we must keep it
disabled for tiny RCU, because it would otherwise pull in a large
amount of code that would make tiny RCU less than tiny.

I ran some file system metadata intensive workloads (git checkout,
FS-Mark) on a variety of machines with this patch and saw no
detectable change in performance.

Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 lib/Kconfig.debug | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index b06848a104e6..5655bd95919a 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1450,6 +1450,7 @@ config RCU_CPU_STALL_TIMEOUT
 config RCU_TRACE
 	bool "Enable tracing for RCU"
 	depends on DEBUG_KERNEL
+	default y if TREE_RCU
 	select TRACE_CLOCK
 	help
 	  This option provides tracing in RCU which presents stats
-- 
2.5.2

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH tip/core/rcu 0/20] Miscellaneous fixes for 4.11 "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-01-14 10:20 +0100
  [PATCH tip/core/rcu 19/20] rcu: Eliminate unused expedited_normal counter "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-01-14 10:20 +0100
  [PATCH tip/core/rcu 12/20] rcu: Re-enable TASKS_RCU for User Mode Linux "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-01-14 10:20 +0100
  [PATCH tip/core/rcu 20/20] rcu: Add lockdep checks to synchronous expedited primitives "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-01-14 10:20 +0100
  [PATCH tip/core/rcu 16/20] rcu: Enable RCU tracepoints by default to aid in debugging "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-01-14 10:20 +0100
  [PATCH tip/core/rcu 03/20] Fix: Disable sys_membarrier when nohz_full is enabled "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-01-14 10:20 +0100
  [PATCH tip/core/rcu 17/20] rcu: Fix comment in rcu_organize_nocb_kthreads() "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-01-14 10:20 +0100
  [PATCH tip/core/rcu 10/20] rcu: Add functions to test for trivial grace periods "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-01-14 10:20 +0100
    Re: [PATCH tip/core/rcu 10/20] rcu: Add functions to test for  trivial grace periods Josh Triplett <josh@joshtriplett.org> - 2017-01-16 09:10 +0100
  [PATCH tip/core/rcu 04/20] rcu: Only dump stalled-tasks stacks if there was a real stall "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-01-14 10:20 +0100
  [PATCH tip/core/rcu 18/20] llist: Clarify comments about when locking is needed "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-01-14 10:20 +0100
  [PATCH tip/core/rcu 15/20] rcu: Make rcu_cpu_starting() use its "cpu" argument "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-01-14 10:20 +0100
  [PATCH tip/core/rcu 05/20] rcu: Remove unneeded rcu_process_callbacks() declarations "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-01-14 10:20 +0100
  [PATCH tip/core/rcu 01/20] rcu: update: Make RCU_EXPEDITE_BOOT be the default "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-01-14 10:20 +0100
  Re: [PATCH tip/core/rcu 0/20] Miscellaneous fixes for 4.11 Josh Triplett <josh@joshtriplett.org> - 2017-01-16 09:20 +0100

csiph-web