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lyphyserandHanzo Dev
26b6f703f1
The deepSleepTimeout/handshakeTimeout thresholds bound how long stub threads and the dispatcher spin before deep-sleeping. They were hardcoded in cputicks() units tuned for the amd64 TSC (~2GHz), e.g. 40000 ticks for "20µs". But cputicks() advances at a platform-specific rate unrelated to the CPU clock: on arm64 it reads CNTVCT_EL0, which runs at CNTFRQ_EL0 -- anywhere from tens of MHz up to ~1GHz depending on the core -- so a fixed tick count maps to a different wall-clock duration there. On a tens-of-MHz part, 40000 ticks is ~2ms (~100x the intended 20µs), so idle stub threads and the dispatcher spin far too long before sleeping, burning CPU on otherwise idle containers (issue #13361). Neither RDTSC nor CNTVCT_EL0 is an instruction/cycle counter; both are constant-rate time references at frequencies that differ per platform, so the timeouts are fundamentally durations. Express them once as nanosecond durations and convert to cputicks() units via a new per-arch cputicksFreq(): - arm64 reads CNTFRQ_EL0 (exact, no calibration). - amd64 returns the nominal 2GHz the constants were tuned against, so amd64 behavior is unchanged. initSleepTimeouts() performs the conversion once in New(), before stubInit() copies deepSleepTimeout into the stub. Co-authored-by: Hanzo Dev <[email protected]>
57 lines
1.9 KiB
Go
57 lines
1.9 KiB
Go
// Copyright 2019 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package systrap
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import (
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"gvisor.dev/gvisor/pkg/sentry/arch"
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)
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func stackPointer(r *arch.Registers) uintptr {
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return uintptr(r.Rsp)
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}
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// nominalTSCFreq is the assumed frequency in Hz of the x86 TSC read by
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// cputicks(). The TSC is invariant (it ticks at a fixed reference rate
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// independent of the core clock), but its exact frequency is not cheaply
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// discoverable, so cputicksFreq() assumes this nominal ~2GHz.
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const nominalTSCFreq = 2 * 1000 * 1000 * 1000
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// cputicksFreq returns the frequency in Hz of the counter read by cputicks().
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func cputicksFreq() uint64 {
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return nominalTSCFreq
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}
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// x86 use the fs_base register to store the TLS pointer which can be
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// get/set in "func (t *thread) get/setRegs(regs *arch.Registers)".
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// So both of the get/setTLS() operations are noop here.
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// getTLS gets the thread local storage register.
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func (t *thread) getTLS(tls *uint64) error {
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return nil
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}
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// setTLS sets the thread local storage register.
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func (t *thread) setTLS(tls *uint64) error {
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return nil
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}
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// configureSystrapAddressSpace is a no-op on amd64.
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//
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// On ARM64, this function overrides the default 48-bit address space
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// parameters to support 39-bit and 52-bit VA widths. On amd64, the
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// address space layout is fixed and does not require dynamic
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// configuration, so this is intentionally empty.
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func configureSystrapAddressSpace() {}
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