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| author | Michael Anthony Knyszek <mknyszek@google.com> | 2020-11-02 19:03:16 +0000 |
|---|---|---|
| committer | Michael Knyszek <mknyszek@google.com> | 2020-11-02 21:21:46 +0000 |
| commit | 39a5ee52b9b41b1e4f4cf821c78ef5b7be68d181 (patch) | |
| tree | 7c1929e087a1d27118dcad9f607391868dbb32a0 /src/runtime/runtime2.go | |
| parent | ac766e37182f36cd0a3247e44a4143d2d2132e42 (diff) | |
| download | go-39a5ee52b9b41b1e4f4cf821c78ef5b7be68d181.tar.gz go-39a5ee52b9b41b1e4f4cf821c78ef5b7be68d181.zip | |
runtime: decouple consistent stats from mcache and allow P-less update
This change modifies the consistent stats implementation to keep the
per-P sequence counter on each P instead of each mcache. A valid mcache
is not available everywhere that we want to call e.g. allocSpan, as per
issue #42339. By decoupling these two, we can add a mechanism to allow
contexts without a P to update stats consistently.
In this CL, we achieve that with a mutex. In practice, it will be very
rare for an M to update these stats without a P. Furthermore, the stats
reader also only needs to hold the mutex across the update to "gen"
since once that changes, writers are free to continue updating the new
stats generation. Contention could thus only arise between writers
without a P, and as mentioned earlier, those should be rare.
A nice side-effect of this change is that the consistent stats acquire
and release API becomes simpler.
Fixes #42339.
Change-Id: Ied74ab256f69abd54b550394c8ad7c4c40a5fe34
Reviewed-on: https://go-review.googlesource.com/c/go/+/267158
Run-TryBot: Michael Knyszek <mknyszek@google.com>
Trust: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Diffstat (limited to 'src/runtime/runtime2.go')
| -rw-r--r-- | src/runtime/runtime2.go | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go index 82fedd804b..c9376827da 100644 --- a/src/runtime/runtime2.go +++ b/src/runtime/runtime2.go @@ -654,8 +654,8 @@ type p struct { timerModifiedEarliest uint64 // Per-P GC state - gcAssistTime int64 // Nanoseconds in assistAlloc - gcFractionalMarkTime int64 // Nanoseconds in fractional mark worker (atomic) + gcAssistTime int64 // Nanoseconds in assistAlloc + gcFractionalMarkTime int64 // Nanoseconds in fractional mark worker (atomic) // gcMarkWorkerMode is the mode for the next mark worker to run in. // That is, this is used to communicate with the worker goroutine @@ -679,6 +679,10 @@ type p struct { runSafePointFn uint32 // if 1, run sched.safePointFn at next safe point + // statsSeq is a counter indicating whether this P is currently + // writing any stats. Its value is even when not, odd when it is. + statsSeq uint32 + // Lock for timers. We normally access the timers while running // on this P, but the scheduler can also do it from a different P. timersLock mutex |