go122-syscall-steal-proc-ambiguous.go

     1  // Copyright 2023 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Tests syscall P stealing.
     6  //
     7  // Specifically, it tests a scenario wherein, without a
     8  // P sequence number of GoSyscallBegin, the syscall that
     9  // a ProcSteal applies to is ambiguous. This only happens in
    10  // practice when the events aren't already properly ordered
    11  // by timestamp, since the ProcSteal won't be seen until after
    12  // the correct GoSyscallBegin appears on the frontier.
    13  
    14  package main
    15  
    16  import (
    17  	"internal/trace"
    18  	"internal/trace/internal/testgen"
    19  	"internal/trace/tracev2"
    20  	"internal/trace/version"
    21  )
    22  
    23  func main() {
    24  	testgen.Main(version.Go122, gen)
    25  }
    26  
    27  func gen(t *testgen.Trace) {
    28  	t.DisableTimestamps()
    29  
    30  	g := t.Generation(1)
    31  
    32  	// One goroutine does a syscall without blocking, then another one where
    33  	// it's P gets stolen.
    34  	b0 := g.Batch(trace.ThreadID(0), 0)
    35  	b0.Event("ProcStatus", trace.ProcID(0), tracev2.ProcRunning)
    36  	b0.Event("GoStatus", trace.GoID(1), trace.ThreadID(0), tracev2.GoRunning)
    37  	b0.Event("GoSyscallBegin", testgen.Seq(1), testgen.NoStack)
    38  	b0.Event("GoSyscallEnd")
    39  	b0.Event("GoSyscallBegin", testgen.Seq(2), testgen.NoStack)
    40  	b0.Event("GoSyscallEndBlocked")
    41  
    42  	// A running goroutine steals proc 0.
    43  	b1 := g.Batch(trace.ThreadID(1), 0)
    44  	b1.Event("ProcStatus", trace.ProcID(2), tracev2.ProcRunning)
    45  	b1.Event("GoStatus", trace.GoID(2), trace.ThreadID(1), tracev2.GoRunning)
    46  	b1.Event("ProcSteal", trace.ProcID(0), testgen.Seq(3), trace.ThreadID(0))
    47  }
    48
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