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From 04dce26bd12888b924425beefa449a07b683021a Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Renaud=20M=C3=A9trich?= <rmetrich@redhat.com>
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Date: Fri, 13 Apr 2018 09:24:30 +0200
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Subject: [PATCH] [kernel] Disable gathering /proc/timer* statistics
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Disable gathering /proc/timer* statistics by default, a new option
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'kernel.with-timer' enables gathering these.
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If /proc/timer_list is huge, then kernel will experience issues with
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processing all the timers since it needs to spin in a tight loop inside
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the kernel.
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We have tried to fix it from kernel side, added touch_nmi_watchdog() to
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silence softlockups, cond_resched() to fix RCU stall issue but with such
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huge number of timers the RHEL7 kernel is still hangs.
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It can reproduced somehow on upstream kernel (however, there will be
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workqueue lockups).
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We came to conclusion that reading /proc/timer_list should be disabled
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in sosreport. Since /proc/timer_stats is tight to /proc/timer_list, both
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are disabled at the same time.
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Resolves: #1268
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Signed-off-by: Renaud Métrich <rmetrich@redhat.com>
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Signed-off-by: Bryn M. Reeves <bmr@redhat.com>
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---
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sos/plugins/kernel.py | 10 +++++++++-
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1 file changed, 9 insertions(+), 1 deletion(-)
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diff --git a/sos/plugins/kernel.py b/sos/plugins/kernel.py
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index 97ef7862..6c2f509c 100644
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--- a/sos/plugins/kernel.py
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+++ b/sos/plugins/kernel.py
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@@ -27,6 +27,10 @@ class Kernel(Plugin, RedHatPlugin, DebianPlugin, UbuntuPlugin):
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sys_module = '/sys/module'
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+ option_list = [
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+ ("with-timer", "gather /proc/timer* statistics", "slow", False)
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+ ]
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+
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def setup(self):
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# compat
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self.add_cmd_output("uname -a", root_symlink="uname")
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@@ -83,7 +87,6 @@ class Kernel(Plugin, RedHatPlugin, DebianPlugin, UbuntuPlugin):
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"/proc/driver",
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"/proc/sys/kernel/tainted",
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"/proc/softirqs",
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- "/proc/timer*",
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"/proc/lock*",
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"/proc/misc",
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"/var/log/dmesg",
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@@ -92,4 +95,9 @@ class Kernel(Plugin, RedHatPlugin, DebianPlugin, UbuntuPlugin):
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clocksource_path + "current_clocksource"
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])
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+ if self.get_option("with-timer"):
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+ # This can be very slow, depending on the number of timers,
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+ # and may also cause softlockups
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+ self.add_copy_spec("/proc/timer*")
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+
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# vim: set et ts=4 sw=4 :
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--
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2.13.6
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