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author | Ingo Molnar <mingo@kernel.org> | 2013-04-26 10:05:59 +0200 |
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committer | Ingo Molnar <mingo@kernel.org> | 2013-04-26 10:13:42 +0200 |
commit | 47aa8b6cbcb839efe2edaa5b50fee21df115d37b (patch) | |
tree | b3c54811c75f40c11ba4344b8089156724d5e074 /Documentation/timers | |
parent | 65e709dc0c25dbd563861924815e9a3a93878b75 (diff) | |
download | linux-stable-47aa8b6cbcb839efe2edaa5b50fee21df115d37b.tar.gz linux-stable-47aa8b6cbcb839efe2edaa5b50fee21df115d37b.tar.bz2 linux-stable-47aa8b6cbcb839efe2edaa5b50fee21df115d37b.zip |
nohz: Reduce overhead under high-freq idling patterns
One testbox of mine (Intel Nehalem, 16-way) uses MWAIT for its idle routine,
which apparently can break out of its idle loop rather frequently, with
high frequency.
In that case NO_HZ_FULL=y kernels show high ksoftirqd overhead and constant
context switching, because tick_nohz_stop_sched_tick() will, if
delta_jiffies == 0, mis-identify this as a timer event - activating the
TIMER_SOFTIRQ, which wakes up ksoftirqd.
Fix this by treating delta_jiffies == 0 the same way we treat other short
wakeups, delta_jiffies == 1.
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'Documentation/timers')
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