This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
[PATCH] Check the HTT bit before counting logical threads
- From: "H.J. Lu" <hongjiu dot lu at intel dot com>
- To: GNU C Library <libc-alpha at sourceware dot org>
- Date: Tue, 17 May 2016 11:02:57 -0700
- Subject: [PATCH] Check the HTT bit before counting logical threads
- Authentication-results: sourceware.org; auth=none
- Reply-to: "H.J. Lu" <hjl dot tools at gmail dot com>
Skip counting logical threads for Intel processors if the HTT bit is 0
which indicates there is only a single logical processor.
Tested on x86. Any comments, feedbacks?
H.J.
---
* sysdeps/x86/cacheinfo.c (init_cacheinfo): Skip counting
logical threads if the HTT bit is 0.
* sysdeps/x86/cpu-features.h (bit_cpu_HTT): New.
(index_cpu_HTT): Likewise.
(reg_HTT): Likewise.
---
sysdeps/x86/cacheinfo.c | 6 ++++++
sysdeps/x86/cpu-features.h | 3 +++
2 files changed, 9 insertions(+)
diff --git a/sysdeps/x86/cacheinfo.c b/sysdeps/x86/cacheinfo.c
index 8408624..09113ba 100644
--- a/sysdeps/x86/cacheinfo.c
+++ b/sysdeps/x86/cacheinfo.c
@@ -506,6 +506,11 @@ init_cacheinfo (void)
shared = core;
}
+ /* A value of 0 for the HTT bit indicates there is only a single
+ logical processor. */
+ if (!HAS_CPU_FEATURE (HTT))
+ goto intel_no_threads;
+
/* Figure out the number of logical threads that share the
highest cache level. */
if (max_cpuid >= 4)
@@ -594,6 +599,7 @@ init_cacheinfo (void)
>> 16) & 0xff);
}
+intel_no_threads:
/* Cap usage of highest cache level to the number of supported
threads. */
if (shared > 0 && threads > 0)
diff --git a/sysdeps/x86/cpu-features.h b/sysdeps/x86/cpu-features.h
index 9529d61..2bd9371 100644
--- a/sysdeps/x86/cpu-features.h
+++ b/sysdeps/x86/cpu-features.h
@@ -51,6 +51,7 @@
#define bit_cpu_POPCOUNT (1 << 23)
#define bit_cpu_FMA (1 << 12)
#define bit_cpu_FMA4 (1 << 16)
+#define bit_cpu_HTT (1 << 28)
/* COMMON_CPUID_INDEX_7. */
#define bit_cpu_ERMS (1 << 9)
@@ -235,6 +236,7 @@ extern const struct cpu_features *__get_cpu_features (void)
# define index_cpu_FMA4 COMMON_CPUID_INDEX_80000001
# define index_cpu_POPCOUNT COMMON_CPUID_INDEX_1
# define index_cpu_OSXSAVE COMMON_CPUID_INDEX_1
+# define index_cpu_HTT COMMON_CPUID_INDEX_1
# define reg_CX8 edx
# define reg_CMOV edx
@@ -252,6 +254,7 @@ extern const struct cpu_features *__get_cpu_features (void)
# define reg_FMA4 ecx
# define reg_POPCOUNT ecx
# define reg_OSXSAVE ecx
+# define reg_HTT edx
# define index_arch_Fast_Rep_String FEATURE_INDEX_1
# define index_arch_Fast_Copy_Backward FEATURE_INDEX_1
--
2.5.5