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| author | Borislav Petkov <bp@suse.de> | 2017-02-05 11:50:21 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-02-05 12:18:45 +0100 |
| commit | 79a8b9aa388b0620cc1d525d7c0f0d9a8a85e08e (patch) | |
| tree | ba8edfc42ad0fe8182879b97fa615436a3a19a53 /arch/x86/include/asm/processor.h | |
| parent | a0a28644c1cf191e514dd64bf438e69c178b8440 (diff) | |
| download | lwn-79a8b9aa388b0620cc1d525d7c0f0d9a8a85e08e.tar.gz lwn-79a8b9aa388b0620cc1d525d7c0f0d9a8a85e08e.zip | |
x86/CPU/AMD: Bring back Compute Unit ID
Commit:
a33d331761bc ("x86/CPU/AMD: Fix Bulldozer topology")
restored the initial approach we had with the Fam15h topology of
enumerating CU (Compute Unit) threads as cores. And this is still
correct - they're beefier than HT threads but still have some
shared functionality.
Our current approach has a problem with the Mad Max Steam game, for
example. Yves Dionne reported a certain "choppiness" while playing on
v4.9.5.
That problem stems most likely from the fact that the CU threads share
resources within one CU and when we schedule to a thread of a different
compute unit, this incurs latency due to migrating the working set to a
different CU through the caches.
When the thread siblings mask mirrors that aspect of the CUs and
threads, the scheduler pays attention to it and tries to schedule within
one CU first. Which takes care of the latency, of course.
Reported-by: Yves Dionne <yves.dionne@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: <stable@vger.kernel.org> # 4.9
Cc: Brice Goglin <Brice.Goglin@inria.fr>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yazen Ghannam <yazen.ghannam@amd.com>
Link: http://lkml.kernel.org/r/20170205105022.8705-1-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include/asm/processor.h')
| -rw-r--r-- | arch/x86/include/asm/processor.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 1be64da0384e..e6cfe7ba2d65 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -104,6 +104,7 @@ struct cpuinfo_x86 { __u8 x86_phys_bits; /* CPUID returned core id bits: */ __u8 x86_coreid_bits; + __u8 cu_id; /* Max extended CPUID function supported: */ __u32 extended_cpuid_level; /* Maximum supported CPUID level, -1=no CPUID: */ |