From: Bruce Richardson <bruce.richardson@intel.com>
To: dev@dpdk.org
Cc: david.marchand@redhat.com, wathsala.vithanage@arm.com,
konstantin.ananyev@huawei.com,
Bruce Richardson <bruce.richardson@intel.com>
Subject: [PATCH] eal/x86: cache queried CPU flags
Date: Fri, 11 Oct 2024 14:31:55 +0100 [thread overview]
Message-ID: <20241011133219.1495983-1-bruce.richardson@intel.com> (raw)
In-Reply-To: <20241007110725.377550-1-bruce.richardson@intel.com>
Rather than re-querying the HW each time a CPU flag is requested, we can
just save the return value in the flags array. This should speed up
repeated querying of CPU flags, and provides a workaround for a reported
issue where errors are seen with constant querying of the AVX-512 CPU
flag from a non-AVX VM.
Bugzilla ID: 1501
Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
---
V2: Add compiler barrier to prevent issues with multi-threaded calls
---
lib/eal/x86/rte_cpuflags.c | 22 +++++++++++++++++-----
1 file changed, 17 insertions(+), 5 deletions(-)
diff --git a/lib/eal/x86/rte_cpuflags.c b/lib/eal/x86/rte_cpuflags.c
index 26163ab746..90389c66fc 100644
--- a/lib/eal/x86/rte_cpuflags.c
+++ b/lib/eal/x86/rte_cpuflags.c
@@ -8,8 +8,10 @@
#include <errno.h>
#include <stdint.h>
#include <string.h>
+#include <stdbool.h>
#include "rte_cpuid.h"
+#include "rte_atomic.h"
/**
* Struct to hold a processor feature entry
@@ -21,12 +23,14 @@ struct feature_entry {
uint32_t bit; /**< cpuid register bit */
#define CPU_FLAG_NAME_MAX_LEN 64
char name[CPU_FLAG_NAME_MAX_LEN]; /**< String for printing */
+ bool has_value;
+ bool value;
};
#define FEAT_DEF(name, leaf, subleaf, reg, bit) \
[RTE_CPUFLAG_##name] = {leaf, subleaf, reg, bit, #name },
-const struct feature_entry rte_cpu_feature_table[] = {
+struct feature_entry rte_cpu_feature_table[] = {
FEAT_DEF(SSE3, 0x00000001, 0, RTE_REG_ECX, 0)
FEAT_DEF(PCLMULQDQ, 0x00000001, 0, RTE_REG_ECX, 1)
FEAT_DEF(DTES64, 0x00000001, 0, RTE_REG_ECX, 2)
@@ -147,7 +151,7 @@ const struct feature_entry rte_cpu_feature_table[] = {
int
rte_cpu_get_flag_enabled(enum rte_cpu_flag_t feature)
{
- const struct feature_entry *feat;
+ struct feature_entry *feat;
cpuid_registers_t regs;
unsigned int maxleaf;
@@ -156,6 +160,8 @@ rte_cpu_get_flag_enabled(enum rte_cpu_flag_t feature)
return -ENOENT;
feat = &rte_cpu_feature_table[feature];
+ if (feat->has_value)
+ return feat->value;
if (!feat->leaf)
/* This entry in the table wasn't filled out! */
@@ -163,8 +169,10 @@ rte_cpu_get_flag_enabled(enum rte_cpu_flag_t feature)
maxleaf = __get_cpuid_max(feat->leaf & 0x80000000, NULL);
- if (maxleaf < feat->leaf)
- return 0;
+ if (maxleaf < feat->leaf) {
+ feat->value = 0;
+ goto out;
+ }
#ifdef RTE_TOOLCHAIN_MSVC
__cpuidex(regs, feat->leaf, feat->subleaf);
@@ -175,7 +183,11 @@ rte_cpu_get_flag_enabled(enum rte_cpu_flag_t feature)
#endif
/* check if the feature is enabled */
- return (regs[feat->reg] >> feat->bit) & 1;
+ feat->value = (regs[feat->reg] >> feat->bit) & 1;
+out:
+ rte_compiler_barrier();
+ feat->has_value = true;
+ return feat->value;
}
const char *
--
2.43.0
next prev parent reply other threads:[~2024-10-11 13:32 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-10-07 11:06 Bruce Richardson
2024-10-07 11:23 ` David Marchand
2024-10-07 14:47 ` Wathsala Wathawana Vithanage
2024-10-07 16:29 ` Wathsala Wathawana Vithanage
2024-10-07 16:43 ` Bruce Richardson
2024-10-07 17:30 ` Wathsala Wathawana Vithanage
2024-10-11 12:42 ` Konstantin Ananyev
2024-10-11 12:48 ` Bruce Richardson
2024-10-11 13:00 ` Konstantin Ananyev
2024-10-11 13:31 ` Bruce Richardson [this message]
2024-10-11 13:33 ` [PATCH v2] " Bruce Richardson
2024-10-11 13:37 ` Konstantin Ananyev
2024-10-14 18:29 ` David Marchand
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20241011133219.1495983-1-bruce.richardson@intel.com \
--to=bruce.richardson@intel.com \
--cc=david.marchand@redhat.com \
--cc=dev@dpdk.org \
--cc=konstantin.ananyev@huawei.com \
--cc=wathsala.vithanage@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).