You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
45 lines
2.1 KiB
45 lines
2.1 KiB
From ed2f9dc9420c4c61436328778a70459d0a35556a Mon Sep 17 00:00:00 2001 |
|
From: Noah Goldstein <goldstein.w.n@gmail.com> |
|
Date: Mon, 8 May 2023 22:10:20 -0500 |
|
Subject: [PATCH] x86: Use 64MB as nt-store threshold if no cacheinfo [BZ |
|
#30429] |
|
Content-type: text/plain; charset=UTF-8 |
|
|
|
If `non_temporal_threshold` is below `minimum_non_temporal_threshold`, |
|
it almost certainly means we failed to read the systems cache info. |
|
|
|
In this case, rather than defaulting the minimum correct value, we |
|
should default to a value that gets at least reasonable |
|
performance. 64MB is chosen conservatively to be at the very high |
|
end. This should never cause non-temporal stores when, if we had read |
|
cache info, we wouldn't have otherwise. |
|
Reviewed-by: Florian Weimer <fweimer@redhat.com> |
|
--- |
|
sysdeps/x86/dl-cacheinfo.h | 10 +++++++++- |
|
1 file changed, 9 insertions(+), 1 deletion(-) |
|
|
|
diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h |
|
index ec88945b39..877e73d700 100644 |
|
--- a/sysdeps/x86/dl-cacheinfo.h |
|
+++ b/sysdeps/x86/dl-cacheinfo.h |
|
@@ -749,8 +749,16 @@ dl_init_cacheinfo (struct cpu_features *cpu_features) |
|
reflected in the manual. */ |
|
unsigned long int maximum_non_temporal_threshold = SIZE_MAX >> 4; |
|
unsigned long int minimum_non_temporal_threshold = 0x4040; |
|
+ |
|
+ /* If `non_temporal_threshold` less than `minimum_non_temporal_threshold` |
|
+ it most likely means we failed to detect the cache info. We don't want |
|
+ to default to `minimum_non_temporal_threshold` as such a small value, |
|
+ while correct, has bad performance. We default to 64MB as reasonable |
|
+ default bound. 64MB is likely conservative in that most/all systems would |
|
+ choose a lower value so it should never forcing non-temporal stores when |
|
+ they otherwise wouldn't be used. */ |
|
if (non_temporal_threshold < minimum_non_temporal_threshold) |
|
- non_temporal_threshold = minimum_non_temporal_threshold; |
|
+ non_temporal_threshold = 64 * 1024 * 1024; |
|
else if (non_temporal_threshold > maximum_non_temporal_threshold) |
|
non_temporal_threshold = maximum_non_temporal_threshold; |
|
|
|
-- |
|
2.39.3 |
|
|
|
|