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authorJamie Liu <jamieliu@google.com>2020-09-02 11:35:18 -0700
committergVisor bot <gvisor-bot@google.com>2020-09-02 11:37:31 -0700
commit9bd01642377eef9d91f9243091b6da28f37d164a (patch)
tree62954e9e307ec32836f42e8000688df94d62ae0f /pkg/tcpip/link/qdisc
parentb9b6660dc4ec0cee77bb30ac7a44c061ada1b3d6 (diff)
Improve sync.SeqCount performance.
- Make sync.SeqCountEpoch not a struct. This allows sync.SeqCount.BeginRead() to be inlined. - Mark sync.SeqAtomicLoad<T> nosplit to mitigate the Go compiler's refusal to inline it. (Best I could get was "cost 92 exceeds budget 80".) - Use runtime-guided spinning in SeqCount.BeginRead(). Benchmarks: name old time/op new time/op delta pkg:pkg/sync/sync goos:linux goarch:amd64 SeqCountWriteUncontended-12 8.24ns ± 0% 11.40ns ± 0% +38.35% (p=0.000 n=10+10) SeqCountReadUncontended-12 0.33ns ± 0% 0.14ns ± 3% -57.77% (p=0.000 n=7+8) pkg:pkg/sync/seqatomictest/seqatomic goos:linux goarch:amd64 SeqAtomicLoadIntUncontended-12 0.64ns ± 1% 0.41ns ± 1% -36.40% (p=0.000 n=10+8) SeqAtomicTryLoadIntUncontended-12 0.18ns ± 4% 0.18ns ± 1% ~ (p=0.206 n=10+8) AtomicValueLoadIntUncontended-12 0.27ns ± 3% 0.27ns ± 0% -1.77% (p=0.000 n=10+8) (atomic.Value.Load is, of course, inlined. We would expect an uncontended inline SeqAtomicLoad<int> to perform identically to SeqAtomicTryLoad<int>.) The "regression" in BenchmarkSeqCountWriteUncontended, despite this CL changing nothing in that path, is attributed to microarchitectural subtlety; the benchmark loop is unchanged except for its address: Before this CL: :0 0x4e62d1 48ffc2 INCQ DX :0 0x4e62d4 48399110010000 CMPQ DX, 0x110(CX) :0 0x4e62db 7e26 JLE 0x4e6303 :0 0x4e62dd 90 NOPL :0 0x4e62de bb01000000 MOVL $0x1, BX :0 0x4e62e3 f00fc118 LOCK XADDL BX, 0(AX) :0 0x4e62e7 ffc3 INCL BX :0 0x4e62e9 0fbae300 BTL $0x0, BX :0 0x4e62ed 733a JAE 0x4e6329 :0 0x4e62ef 90 NOPL :0 0x4e62f0 bb01000000 MOVL $0x1, BX :0 0x4e62f5 f00fc118 LOCK XADDL BX, 0(AX) :0 0x4e62f9 ffc3 INCL BX :0 0x4e62fb 0fbae300 BTL $0x0, BX :0 0x4e62ff 73d0 JAE 0x4e62d1 After this CL: :0 0x4e6361 48ffc2 INCQ DX :0 0x4e6364 48399110010000 CMPQ DX, 0x110(CX) :0 0x4e636b 7e26 JLE 0x4e6393 :0 0x4e636d 90 NOPL :0 0x4e636e bb01000000 MOVL $0x1, BX :0 0x4e6373 f00fc118 LOCK XADDL BX, 0(AX) :0 0x4e6377 ffc3 INCL BX :0 0x4e6379 0fbae300 BTL $0x0, BX :0 0x4e637d 733a JAE 0x4e63b9 :0 0x4e637f 90 NOPL :0 0x4e6380 bb01000000 MOVL $0x1, BX :0 0x4e6385 f00fc118 LOCK XADDL BX, 0(AX) :0 0x4e6389 ffc3 INCL BX :0 0x4e638b 0fbae300 BTL $0x0, BX :0 0x4e638f 73d0 JAE 0x4e6361 PiperOrigin-RevId: 329754148
Diffstat (limited to 'pkg/tcpip/link/qdisc')
0 files changed, 0 insertions, 0 deletions