From a3582de6186edcc88e022af2b9f9c1cef90e44ed Mon Sep 17 00:00:00 2001
From: gVisor bot <gvisor-bot@google.com>
Date: Tue, 18 Feb 2020 13:49:17 -0800
Subject: cpuid: cache the maximum size of xsave state
perf shows that ExtendedStateSize cosumes more than 20% of cpu:
23.61% 23.61% [.] pkg/cpuid/cpuid.HostID
PiperOrigin-RevId: 295813263
---
pkg/cpuid/cpuid_x86.go | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)
diff --git a/pkg/cpuid/cpuid_x86.go b/pkg/cpuid/cpuid_x86.go
index 333ca0a04..a0bc55ea1 100644
--- a/pkg/cpuid/cpuid_x86.go
+++ b/pkg/cpuid/cpuid_x86.go
@@ -725,6 +725,18 @@ func vendorIDFromRegs(bx, cx, dx uint32) string {
return string(bytes)
}
+var maxXsaveSize = func() uint32 {
+ // Leaf 0 of xsaveinfo function returns the size for currently
+ // enabled xsave features in ebx, the maximum size if all valid
+ // features are saved with xsave in ecx, and valid XCR0 bits in
+ // edx:eax.
+ //
+ // If xSaveInfo isn't supported, cpuid will not fault but will
+ // return bogus values.
+ _, _, maxXsaveSize, _ := HostID(uint32(xSaveInfo), 0)
+ return maxXsaveSize
+}()
+
// ExtendedStateSize returns the number of bytes needed to save the "extended
// state" for this processor and the boundary it must be aligned to. Extended
// state includes floating point registers, and other cpu state that's not
@@ -736,12 +748,7 @@ func vendorIDFromRegs(bx, cx, dx uint32) string {
// about 2.5K worst case, with avx512).
func (fs *FeatureSet) ExtendedStateSize() (size, align uint) {
if fs.UseXsave() {
- // Leaf 0 of xsaveinfo function returns the size for currently
- // enabled xsave features in ebx, the maximum size if all valid
- // features are saved with xsave in ecx, and valid XCR0 bits in
- // edx:eax.
- _, _, maxSize, _ := HostID(uint32(xSaveInfo), 0)
- return uint(maxSize), 64
+ return uint(maxXsaveSize), 64
}
// If we don't support xsave, we fall back to fxsave, which requires
--
cgit v1.2.3