The following commit has been merged into the sched/urgent branch of tip:
Commit-ID: 23ccee22e834eca236b9a20989caf6905bd6954a
Gitweb: https://git.kernel.org/tip/23ccee22e834eca236b9a20989caf6905bd6954a
Author: Giovanni Gherdovich <ggherdovich@xxxxxxx>
AuthorDate: Thu, 16 Apr 2020 07:47:43 +02:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Wed, 22 Apr 2020 23:10:13 +02:00
x86, sched: Account for CPUs with less than 4 cores in freq. invariance
If a CPU has less than 4 physical cores, MSR_TURBO_RATIO_LIMIT will
rightfully report that the 4C turbo ratio is zero. In such cases, use the
1C turbo ratio instead for frequency invariance calculations.
Fixes: 1567c3e3467c ("x86, sched: Add support for frequency invariance")
Reported-by: Like Xu <like.xu@xxxxxxxxxxxxxxx>
Reported-by: Neil Rickert <nwr10cst-oslnx@xxxxxxxxx>
Signed-off-by: Giovanni Gherdovich <ggherdovich@xxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Tested-by: Dave Kleikamp <dave.kleikamp@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200416054745.740-3-ggherdovich@xxxxxxx
---
arch/x86/kernel/smpboot.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 3a318ec..5d346b7 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1945,18 +1945,23 @@ static bool skx_set_max_freq_ratio(u64 *base_freq, u64 *turbo_freq, int size)
static bool core_set_max_freq_ratio(u64 *base_freq, u64 *turbo_freq)
{
+ u64 msr;
int err;
err = rdmsrl_safe(MSR_PLATFORM_INFO, base_freq);
if (err)
return false;
- err = rdmsrl_safe(MSR_TURBO_RATIO_LIMIT, turbo_freq);
+ err = rdmsrl_safe(MSR_TURBO_RATIO_LIMIT, &msr);
if (err)
return false;
- *base_freq = (*base_freq >> 8) & 0xFF; /* max P state */
- *turbo_freq = (*turbo_freq >> 24) & 0xFF; /* 4C turbo */
+ *base_freq = (*base_freq >> 8) & 0xFF; /* max P state */
+ *turbo_freq = (msr >> 24) & 0xFF; /* 4C turbo */
+
+ /* The CPU may have less than 4 cores */
+ if (!*turbo_freq)
+ *turbo_freq = msr & 0xFF; /* 1C turbo */
return true;
}
|