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Re: [PATCH for-4.22] Revert "xen/cpufreq: fix usages of align_timer() in the on-demand governor"
- To: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>
- From: Jason Andryuk <jason.andryuk@xxxxxxx>
- Date: Tue, 16 Jun 2026 10:33:12 -0400
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- Cc: <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Tue, 16 Jun 2026 14:33:29 +0000
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On 2026-06-16 03:31, Oleksii Kurochko wrote:
On 6/16/26 8:47 AM, Roger Pau Monné wrote:
On Tue, Jun 16, 2026 at 08:30:25AM +0200, Jan Beulich wrote:
On 15.06.2026 21:39, Jason Andryuk wrote:
The original commit showed a ~6% regression in a benchmark. The
call to
align_timer(firsttick, period) rounds firsttick up to the next mutiple
of the period, if firsttick % period != 0:
align_timer(0, period) -> 0
align_timer(1, period) -> period
align_timer(period, period) -> period
align_timer(period + 1, period) -> 2 * period
So adding the period (sampling_rate) before calling align_timer() will
in most cases incease the expiration to 2 * period (sampling_rate) (the
exception being firsttick % period == 0). This longer timer slows the
reaction time of the algorithm.
This reverts commit a0ed5bcfbeee81c91c574ad484faa057054eaf09.
Signed-off-by: Jason Andryuk <jason.andryuk@xxxxxxx>
Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Adding Oleksii for a release-ack.
Release-Acked-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
Thanks everyone.
Sorry for forgetting to CC you, Oleskii, and mark as for-4.22.
add_maintainers.pl does the right thing... except during the code freeze.
Jan, thanks for fixing up the indent.
Regards,
Jason
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