RE: [PATCH v2] cpufreq: x86: Make scaling_cur_freq behave more as expected

From	"Doug Smythies" <dsmythies@telus.net>
Newsgroups	linux.kernel
Subject	RE: [PATCH v2] cpufreq: x86: Make scaling_cur_freq behave more as expected
Date	2017-08-01 01:50 +0200
Message-ID	<u9sBH-4b7-3@gated-at.bofh.it> (permalink)
References	<tVLEd-3Fl-3@gated-at.bofh.it> <u7gOm-s4-17@gated-at.bofh.it> <u81kd-4Lf-3@gated-at.bofh.it> <u9sBH-4b7-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On 2017.07.28 05:45 Rafael J. Wysocki wrote:

> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> After commit f8475cef9008 "x86: use common aperfmperf_khz_on_cpu() to
> calculate KHz using APERF/MPERF" the scaling_cur_freq policy attribute
> in sysfs only behaves as expected on x86 with APERF/MPERF registers
> available when it is read from at least twice in a row.  The value
> returned by the first read may not be meaningful, because the
> computations in there use cached values from the previous iteration
> of aperfmperf_snapshot_khz() which may be stale.
>
> To prevent that from happening, modify arch_freq_get_on_cpu() to
> call aperfmperf_snapshot_khz() twice, with a short delay between
> these calls, if the previous invocation of aperfmperf_snapshot_khz()
> was too far back in the past (specifically, more that 1s ago).

...[deleted the rest]...

This patch seems to work fine and addresses my complaints from last week.
Thanks.

... Doug

Back to linux.kernel | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

RE: [PATCH v2] cpufreq: x86: Make scaling_cur_freq behave more as expected "Doug Smythies" <dsmythies@telus.net> - 2017-08-01 01:50 +0200
  Re: [PATCH v2] cpufreq: x86: Make scaling_cur_freq behave more as expected "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-08-01 03:00 +0200

csiph-web