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unix: add CPUSetDynamic for systems with more than 1024 CPUs

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The existing CPUSet type is a fixed-size array limited to 1024 CPUs,
which makes it problematic to use for large systems (such as Google's
X4 instances with 1440 and 1920 vCPUs), see e.g.
https://github.com/opencontainers/runc/issues/5023.

Introduce CPUSetDynamic type and NewCPUSet constructor to support large
systems. The bit-managing routines (set/clear/isset/fill/count) are
separated and reused.

Add variants of SchedGetaffinity, SchedSetaffinity and SetMemPolicy
that accept the new type.

Amend the documentation for CPUSet.

Amend the existing TestSchedSetaffinity to:
 - test set.Fill;
 - use t.Cleanup to restore the affinity.

Add tests for new functionality (mostly a copy of existing tests).

This is an alternative to CL 727540 / CL 727541.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
Change-Id: I51bba0305b8dfa7a88a4e7fb8758d73f798574f1
Reviewed-on: https://go-review.googlesource.com/c/sys/+/735380
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
This commit is contained in:
Kir Kolyshkin
2026-04-08 16:32:30 -07:00
committed by Kirill Kolyshkin
co-authored by Claude Sonnet 4.5
parent f33a730cd0
commit 690c91f6ec
4 changed files with 216 additions and 23 deletions
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unix/syscall_linux.go
+6 -2
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@@ -2644,8 +2644,12 @@ func SchedGetAttr(pid int, flags uint) (*SchedAttr, error) {
//sys Cachestat(fd uint, crange *CachestatRange, cstat *Cachestat_t, flags uint) (err error)
//sys Mseal(b []byte, flags uint) (err error)
//sys setMemPolicy(mode int, mask *CPUSet, size int) (err error) = SYS_SET_MEMPOLICY
//sys setMemPolicy(mode int, mask unsafe.Pointer, size uintptr) (err error) = SYS_SET_MEMPOLICY
func SetMemPolicy(mode int, mask *CPUSet) error {
return setMemPolicy(mode, mask, _CPU_SETSIZE)
return setMemPolicy(mode, unsafe.Pointer(mask), _CPU_SETSIZE)
}
func SetMemPolicyDynamic(mode int, mask CPUSetDynamic) error {
return setMemPolicy(mode, mask.pointer(), mask.size())
}