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clocksource: Reduce the default clocksource_watchdog() retries to 2 

With the previous patch, there is an extra watchdog read in each retry.
Now the total number of clocksource reads is increased to 4 per iteration.
In order to avoid increasing the clock skew check overhead, the default
maximum number of retries is reduced from 3 to 2 to maintain the same 12
clocksource reads in the worst case.

Suggested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Waiman Long 2021-11-18 14:14:37 -05:00 committed by Paul E. McKenney
parent c86ff8c55b
commit 1a5620671a
2 changed files with 3 additions and 3 deletions
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4
Documentation/admin-guide/kernel-parameters.txt
View File

@ -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

2
kernel/time/clocksource.c
View File

@ -199,7 +199,7 @@ void clocksource_mark_unstable(struct clocksource *cs)
spin_unlock_irqrestore(&watchdog_lock, flags);
}
ulong max_cswd_read_retries = 3;
ulong max_cswd_read_retries = 2;
module_param(max_cswd_read_retries, ulong, 0644);
EXPORT_SYMBOL_GPL(max_cswd_read_retries);
static int verify_n_cpus = 8;