lkml.org 
[lkml]   [2020]   [May]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v2 2/3] x86, sched: Bail out of frequency invariance if turbo frequency is unknown
Date
There may be CPUs that support turbo boost but don't declare any turbo
ratio, i.e. their MSR_TURBO_RATIO_LIMIT is all zeroes. In that condition
scale-invariant calculations can't be performed.

Signed-off-by: Giovanni Gherdovich <ggherdovich@suse.cz>
Suggested-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Fixes: 1567c3e3467c ("x86, sched: Add support for frequency invariance")
---
arch/x86/kernel/smpboot.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index d660966d7de7..fe154c8226ba 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -2001,9 +2001,11 @@ static bool intel_set_max_freq_ratio(void)
/*
* Some hypervisors advertise X86_FEATURE_APERFMPERF
* but then fill all MSR's with zeroes.
+ * Some CPUs have turbo boost but don't declare any turbo ratio
+ * in MSR_TURBO_RATIO_LIMIT.
*/
- if (!base_freq) {
- pr_debug("Couldn't determine cpu base frequency, necessary for scale-invariant accounting.\n");
+ if (!base_freq || !turbo_freq) {
+ pr_debug("Couldn't determine cpu base or turbo frequency, necessary for scale-invariant accounting.\n");
return false;
}

--
2.16.4
\
 
 \ /
  Last update: 2020-05-31 20:26    [W:0.101 / U:4.096 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site