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Merge branch 'clocksource' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into timers/core

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Pull clocksource watchdog updates from Paul McKenney:

 - Avoid accidental unstable marking of clocksources by rejecting
   clocksource measurements where the source of the skew is the delay
   reading reference clocksource itself.  This change avoids many of the
   current false positives caused by epic cache-thrashing workloads.

 - Reduce the default clocksource_watchdog() retries to 2, thus offsetting
   the increased overhead due to #1 above rereading the reference
   clocksource.

Link: https://lore.kernel.org/lkml/20220105001723.GA536708@paulmck-ThinkPad-P17-Gen-1
This commit is contained in:
Thomas Gleixner
2022-01-10 13:57:17 +01:00
parent 6629c07699 1a5620671a
commit 35e13e9da9
7 changed files with 49 additions and 12 deletions
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4
Documentation/admin-guide/kernel-parameters.txt
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@@ -603,8 +603,8 @@
clocksource.max_cswd_read_retries= [KNL]
Number of clocksource_watchdog() retries due to
external delays before the clock will be marked
unstable. Defaults to three retries, that is,
four attempts to read the clock under test.
unstable. Defaults to two retries, that is,
three attempts to read the clock under test.
clocksource.verify_n_cpus= [KNL]
Limit the number of CPUs checked for clocksources