From: "H.J. Lu" <hjl.tools@gmail.com>
To: libc-alpha@sourceware.org
Cc: Noah Goldstein <goldstein.w.n@gmail.com>
Subject: [PATCH] x86: Check the minimum non_temporal_threshold [BZ #29953]
Date: Tue, 3 Jan 2023 11:37:15 -0800 [thread overview]
Message-ID: <20230103193715.2549830-1-hjl.tools@gmail.com> (raw)
The minimum non_temporal_threshold is 0x4040. non_temporal_threshold may
be set to less than the minimum value when the shared cache size isn't
available (e.g., in an emulator) or by the tunable. Add a check for
the minimum non_temporal_threshold.
This fixes BZ #29953.
---
sysdeps/x86/dl-cacheinfo.h | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)
diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
index e9f3382108..92e8e40752 100644
--- a/sysdeps/x86/dl-cacheinfo.h
+++ b/sysdeps/x86/dl-cacheinfo.h
@@ -861,8 +861,18 @@ dl_init_cacheinfo (struct cpu_features *cpu_features)
share of the cache, it has a substantial risk of negatively
impacting the performance of other threads running on the chip. */
unsigned long int non_temporal_threshold = shared * 3 / 4;
+ /* SIZE_MAX >> 4 because memmove-vec-unaligned-erms right-shifts the value of
+ 'x86_non_temporal_threshold' by `LOG_4X_MEMCPY_THRESH` (4) and it is best
+ if that operation cannot overflow. Minimum of 0x4040 (16448) because the
+ L(large_memset_4x) loops need 64-byte to cache align and enough space for
+ at least 1 iteration of 4x PAGE_SIZE unrolled loop. Both values are
+ reflected in the manual. */
+ unsigned long int minimum_non_temporal_threshold = 0x4040;
+ if (non_temporal_threshold < minimum_non_temporal_threshold)
+ non_temporal_threshold = minimum_non_temporal_threshold;
#if HAVE_TUNABLES
+ unsigned long int maximum_non_temporal_threshold = SIZE_MAX >> 4;
/* NB: The REP MOVSB threshold must be greater than VEC_SIZE * 8. */
unsigned int minimum_rep_movsb_threshold;
#endif
@@ -915,8 +925,8 @@ dl_init_cacheinfo (struct cpu_features *cpu_features)
shared = tunable_size;
tunable_size = TUNABLE_GET (x86_non_temporal_threshold, long int, NULL);
- /* NB: Ignore the default value 0. */
- if (tunable_size != 0)
+ if (tunable_size > minimum_non_temporal_threshold
+ && tunable_size <= maximum_non_temporal_threshold)
non_temporal_threshold = tunable_size;
tunable_size = TUNABLE_GET (x86_rep_movsb_threshold, long int, NULL);
@@ -931,14 +941,9 @@ dl_init_cacheinfo (struct cpu_features *cpu_features)
TUNABLE_SET_WITH_BOUNDS (x86_data_cache_size, data, 0, SIZE_MAX);
TUNABLE_SET_WITH_BOUNDS (x86_shared_cache_size, shared, 0, SIZE_MAX);
- /* SIZE_MAX >> 4 because memmove-vec-unaligned-erms right-shifts the value of
- 'x86_non_temporal_threshold' by `LOG_4X_MEMCPY_THRESH` (4) and it is best
- if that operation cannot overflow. Minimum of 0x4040 (16448) because the
- L(large_memset_4x) loops need 64-byte to cache align and enough space for
- at least 1 iteration of 4x PAGE_SIZE unrolled loop. Both values are
- reflected in the manual. */
TUNABLE_SET_WITH_BOUNDS (x86_non_temporal_threshold, non_temporal_threshold,
- 0x4040, SIZE_MAX >> 4);
+ minimum_non_temporal_threshold,
+ maximum_non_temporal_threshold);
TUNABLE_SET_WITH_BOUNDS (x86_rep_movsb_threshold, rep_movsb_threshold,
minimum_rep_movsb_threshold, SIZE_MAX);
TUNABLE_SET_WITH_BOUNDS (x86_rep_stosb_threshold, rep_stosb_threshold, 1,
--
2.39.0
next reply other threads:[~2023-01-03 19:37 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-03 19:37 H.J. Lu [this message]
2023-01-03 20:24 ` Noah Goldstein
2023-01-03 20:49 ` H.J. Lu
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