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x86, sched: Account for CPUs with less than 4 cores in freq. invariance

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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: 1567c3e346 ("x86, sched: Add support for frequency invariance")
Reported-by: Like Xu <like.xu@linux.intel.com>
Reported-by: Neil Rickert <nwr10cst-oslnx@yahoo.com>
Signed-off-by: Giovanni Gherdovich <ggherdovich@suse.cz>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Link: https://lkml.kernel.org/r/20200416054745.740-3-ggherdovich@suse.cz
This commit is contained in:
Giovanni Gherdovich 2020-04-16 07:47:43 +02:00 committed by Peter Zijlstra
parent 9a6c2c3c7a
commit 23ccee22e8
1 changed files with 8 additions and 3 deletions
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11
arch/x86/kernel/smpboot.c
View file

@ -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;
}