diff options
| 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/kernel/cpu/amd.c | |
| parent | a0a28644c1cf191e514dd64bf438e69c178b8440 (diff) | |
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/kernel/cpu/amd.c')
| -rw-r--r-- | arch/x86/kernel/cpu/amd.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index 1d3167269a67..20dc44d1e6be 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -309,8 +309,15 @@ static void amd_get_topology(struct cpuinfo_x86 *c) /* get information required for multi-node processors */ if (boot_cpu_has(X86_FEATURE_TOPOEXT)) { + u32 eax, ebx, ecx, edx; - node_id = cpuid_ecx(0x8000001e) & 7; + cpuid(0x8000001e, &eax, &ebx, &ecx, &edx); + + node_id = ecx & 0xff; + smp_num_siblings = ((ebx >> 8) & 0xff) + 1; + + if (c->x86 == 0x15) + c->cu_id = ebx & 0xff; /* * We may have multiple LLCs if L3 caches exist, so check if we |