s390/cpum_sf: Rework sampling buffer allocation

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Adjust sampling buffer allocation depending on
frequency and correct comments. Investigation on the
interrupt handler revealed that almost always one interupt
services one SDB, even when running with the maximum frequency
of 100000. Very rarely there have been 2 SBD serviced per
interrupt.

Therefore reduce the number of SBD per CPU. Each SDB is one
page in size. The new formula results in
freq:4000	n_sdb:32	new:16
freq:10000	n_sdb:80	new:16
freq:20000	n_sdb:159	new:17
freq:40000	n_sdb:318	new:19
freq:50000	n_sdb:397	new:20
freq:62500	n_sdb:497	new:22
freq:83333	n_sdb:662	new:24
freq:100000	n_sdb:794	new:25

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

...

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Thomas Richter 2019-12-04 09:29:20 +01:00 • committed by Vasily Gorbik

parent 11a48a5a18

commit 0d6f1693f2

1 changed files with 21 additions and 19 deletions

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arch/s390/kernel/perf_cpum_sf.c

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