Currently the execution tracer synchronizes with itself using very
heavyweight operations. As a result, it's totally fine for most of the
tracer code to look like:

    if traceEnabled() {
	traceXXX(...)
    }

However, if we want to make that synchronization more lightweight (as
issue #60773 proposes), then this is insufficient. In particular, we
need to make sure the tracer can't observe an inconsistency between g
atomicstatus and the event that would be emitted for a particular
g transition. This means making the g status change appear to happen
atomically with the corresponding trace event being written out from the
perspective of the tracer.

This requires a change in API to something more like a lock. While we're
here, we might as well make sure that trace events can *only* be emitted
while this lock is held. This change introduces such an API:
traceAcquire, which returns a value that can emit events, and
traceRelease, which requires the value that was returned by
traceAcquire. In practice, this won't be a real lock, it'll be more like
a seqlock.

For the current tracer, this API is completely overkill and the value
returned by traceAcquire basically just checks trace.enabled. But it's
necessary for the tracer described in #60773 and we can implement that
more cleanly if we do this refactoring now instead of later.

For #60773.

Change-Id: Ibb9ff5958376339fafc2b5180aef65cf2ba18646
Reviewed-on: https://go-review.googlesource.com/c/go/+/515635
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This change mostly implements the design described in #60773 and
includes a new scalable parser for the new trace format, available in
internal/trace/v2. I'll leave this commit message short because this is
clearly an enormous CL with a lot of detail.

This change does not hook up the new tracer into cmd/trace yet. A
follow-up CL will handle that.

For #60773.

Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest,gotip-linux-amd64-longtest-race
Change-Id: I5d2aca2cc07580ed3c76a9813ac48ec96b157de0
Reviewed-on: https://go-review.googlesource.com/c/go/+/494187
Reviewed-by: Michael Pratt <mpratt@google.com>
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This change adds a new MutatorUtilization for traces for Go 1.22+.

To facilitate testing, it also generates a short trace with the
gc-stress.go test program (shortening its duration to 10ms) and adds it
to the tests for the internal/trace/v2 package. Notably, we make sure
this trace has a GCMarkAssistActive event to test that codepath.

For #63960.
For #60773.

Change-Id: I2e61f545988677be716818e2a08641c54c4c201f
Reviewed-on: https://go-review.googlesource.com/c/go/+/540256
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
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This is a complete fork and most of a rewrite of the goroutine analysis
pages for v2 traces. It fixes an issue with the old page where GC time
didn't really make any sense, generalizes the page and breaks things
down further, and adds clarifying text.

This change also modifies the SummarizeGoroutines API to not stream the
trace. This is unfortunate, but we're already reading and holding the
entire trace in memory for the trace viewer. We can revisit this
decision in the future. Also, we want to do this now because the
GoroutineSummary holds on to pointers to events, and these events will
be used by the user region and user task analyses. While tracev2 events
are values and they should be equivalent no matter how many times we
parse a trace, this lets us reference the event in the slice directly.

For #60773.
For #63960.
Fixes #62443.

Change-Id: I1c5ab68141869378843f4f2826686038e4533090
Reviewed-on: https://go-review.googlesource.com/c/go/+/541257
Reviewed-by: Michael Pratt <mpratt@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
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This change moves the MMU HTTP handlers and functionality into the
traceviewer package, since unlike the goroutine pages the vast majority
of that functionality is identical between v1 and v2. This change
involves some refactoring so that callers can plug in their own mutator
utilization computation functions (which is the only point of difference
between v1 and v2). The new interface isn't especially nice, but part of
the problem is the MMU handlers depend on specific endpoints to exist. A
follow-up CL will clean this up a bit.

Like the previous CL did for goroutine analysis, modify the v2 mutator
utilization API to accept a slice of trace events. Again, we might as
well reuse what was already parsed and will be needed for other
purposes. It also simplifies the API slightly.

For #60773.
For #63960.

Change-Id: I6c21ec8d1bf7e95eff5363d0e0005c9217fa00e7
Reviewed-on: https://go-review.googlesource.com/c/go/+/541258
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The last change made the MMU rendering code common and introduced a new
API, but it was kind of messy. Part of the problem was that some of the
Javascript in the template for the main page referred to specific
endpoints on the server.

Fix this by having the Javascript access the same endpoint but with a
different query variable. Now the Javascript code doesn't depend on
specific endpoints, just on query variables for the current endpoint.

For #60773.
For #63960.

Change-Id: I1c559d9859c3a0d62e2094c9d4ab117890b63b31
Reviewed-on: https://go-review.googlesource.com/c/go/+/541259
Auto-Submit: Michael Knyszek <mknyszek@google.com>
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For #60773.
For #63960.

Change-Id: Id97380f19267ec765b25a703ea3e2f284396ad75
Reviewed-on: https://go-review.googlesource.com/c/go/+/541998
Auto-Submit: Michael Knyszek <mknyszek@google.com>
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Reviewed-by: Michael Pratt <mpratt@google.com>

This change adds support for the pprof endpoints to cmd/trace/v2.

In the process, I realized we need to pass the goroutine summaries to
more places, and previous CLs had already done the goroutine analysis
during cmd/trace startup. This change thus refactors the goroutine
analysis API once again to operate in a streaming manner, and to run
at the same time as the initial trace parsing. Now we can include it in
the parsedTrace type and pass that around as the de-facto global trace
context.

Note: for simplicity, this change redefines "syscall" profiles to
capture *all* syscalls, not just syscalls that block. IIUC, this choice
was partly the result of a limitation in the previous trace format that
syscalls don't all have complete durations and many short syscalls are
treated as instant. To this end, this change modifies the text on the
main trace webpage to reflect this change.

For #60773.
For #63960.

Change-Id: I601d9250ab0849a0bfaef233fd9b1e81aca9a22a
Reviewed-on: https://go-review.googlesource.com/c/go/+/541999
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

The v2 trace parser currently handles task inheritance and region task
association incorrectly. It assumes that a TaskID of 0 means that there
is no task. However, this is only true for task events. A TaskID of 0
means that a region gets assigned to the "background task." The parser
currently has no concept of a "background task."

Fix this by defining the background task as task ID 0 and redefining
NoTask to ^uint64(0). This aligns the TaskID values more closely with
other IDs in the parser and also enables disambiguating these two cases.

For #60773.
For #63960.

Change-Id: I09c8217b33b87c8f8f8ea3b0203ed83fd3b61e11
Reviewed-on: https://go-review.googlesource.com/c/go/+/543019
Reviewed-by: Michael Pratt <mpratt@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
TryBot-Bypass: Michael Knyszek <mknyszek@google.com>

For v1 traces, cmd/trace contains code for analyzing tasks separately
from the goroutine analysis code present in internal/trace. As I started
to look into porting that code to v2 traces, I noticed that it wouldn't
be too hard to just generalize the existing v2 goroutine summary code to
generate exactly the same information.

This change does exactly that.

For #60773.
For #63960.

Change-Id: I0cdd9bf9ba11fb292a9ffc37dbf18c2a6a2483b8
Reviewed-on: https://go-review.googlesource.com/c/go/+/542076
Auto-Submit: Michael Knyszek <mknyszek@google.com>
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This code will be useful for the new tracer, and there's no need to
duplicate it. This change copies it to internal/trace/traceviewer, adds
some comments, and renames it to TimeHistogram.

While we're here, let's get rid of the unused String method which has a
comment talking about how awful the rendering is.

Also, let's get rid of uses of niceDuration. We'd have to bring it
with us in the move and I don't think it's worth it. The difference
between the default time.Duration rendering and the niceDuration
rendering is usually a few extra digits of precision. Yes, it's noisier,
but AFAICT it's not substantially worse. It doesn't seem worth the new
API, even if it's just internal. We can also always bring it back later.

For #60773.
For #63960.

Change-Id: I795f58f579f1d503c540c3a40bed12e52bce38e2
Reviewed-on: https://go-review.googlesource.com/c/go/+/542001
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Reviewed-by: Michael Pratt <mpratt@google.com>

This change fills out the last of cmd/trace's subpages for v2 traces by
adding support for task and region endpoints.

For #60773.
For #63960.

Change-Id: Ifc4c660514b3904788785a1b20e3abc3bb9e55f1
Reviewed-on: https://go-review.googlesource.com/c/go/+/542077
Reviewed-by: Michael Pratt <mpratt@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
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This change adds support for the trace?goid=<goid> endpoint to the trace
tool for v2 traces.

In effect, this change actually implements a per-goroutine view. I tried
to add a link to the main page to enable a "view by goroutines" view
without filtering, but the web trace viewer broke the browser tab when
there were a few hundred goroutines. The risk of a browser hang probably
isn't worth the cases where this is nice, especially since filtering by
goroutine already works. Unfortunate, but c'est l'vie. Might be worth
revisiting if we change out the web viewer in the future.

For #60773.
For #63960.

Change-Id: I8e29f4ab8346af6708fd8824505c30f2c43db796
Reviewed-on: https://go-review.googlesource.com/c/go/+/543595
TryBot-Bypass: Michael Knyszek <mknyszek@google.com>
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This change implements support for the trace?focustask=<taskid> endpoint
in the trace tool for v2 traces.

Note: the one missing feature in v2 vs. v1 is that the "irrelevant" (but
still rendered) events are not grayed out. This basically includes
events that overlapped with events that overlapped with other events
that were in the task time period, but aren't themselves directly
associated. This is probably fine -- the UI already puts a very obvious
focus on the period of time the selected task was running.

For #60773.
For #63960.

Change-Id: I5c78a220ae816e331b74cb67c01c5cd98be40dd4
Reviewed-on: https://go-review.googlesource.com/c/go/+/543596
Auto-Submit: Michael Knyszek <mknyszek@google.com>
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This is a nice-to-have that's now straightforward to do with the new
trace format. This change adds a new query variable passed to the
/trace endpoint called "view," which indicates the type of view to
use. It is orthogonal with task-related views.

Unfortunately a goroutine-based view isn't included because it's too
likely to cause the browser tab to crash.

For #60773.
For #63960.

Change-Id: Ifbcb8f2d58ffd425819bdb09c586819cb786478d
Reviewed-on: https://go-review.googlesource.com/c/go/+/543695
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This change adds support for a goroutine-oriented task view via the
/trace?taskid=<taskid> endpoint. This works but it's missing regions.
That will be implemented in a follow-up CL.

For #60773.
For #63960.

Change-Id: I086694143e5c71596ac22fc551416868f0b80923
Reviewed-on: https://go-review.googlesource.com/c/go/+/543937
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This change emits regions in the goroutine-oriented task view (the
/trace endpoint with the taskid query variable set) in the same way the
old cmd/trace does.

For #60773.
Fixes #63960.

Change-Id: If6c3e7072c694c84a7d2d6c34df668f48d3acc2a
Reviewed-on: https://go-review.googlesource.com/c/go/+/543995
Reviewed-by: Michael Pratt <mpratt@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
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For #60773.
For #62627.
For #63960.

For #61422.

Change-Id: I3c933f7522f65cd36d11d38a268556d92c8053f9
Reviewed-on: https://go-review.googlesource.com/c/go/+/546026
Reviewed-by: Michael Pratt <mpratt@google.com>
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For golang#60773.
For golang#62627.
For golang#63960.

For golang#61422.

Change-Id: I3c933f7522f65cd36d11d38a268556d92c8053f9
Reviewed-on: https://go-review.googlesource.com/c/go/+/546026
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For golang/go#60773.

Change-Id: I0f35c07941b5ebafc4e57db037a4a92092d6c7b0
Reviewed-on: https://go-review.googlesource.com/c/proposal/+/503038
Reviewed-by: Michael Pratt <mpratt@google.com>

This change makes the new execution tracer described in #60773, the
default tracer. This change attempts to make the smallest amount of
changes for a single CL.

Updates #66703
For #60773

Change-Id: I3742f3419c54f07d7c020ae5e1c18d29d8bcae6d
Reviewed-on: https://go-review.googlesource.com/c/go/+/576256
Reviewed-by: Michael Knyszek <mknyszek@google.com>
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This change renames the v2 execution tracer files created as part of

Updates #66703
For #60773

Change-Id: I91bfdc08fec4ec68ff3a6e8b5c86f6f8bcae6e6d
Reviewed-on: https://go-review.googlesource.com/c/go/+/576257
Auto-Submit: Carlos Amedee <carlos@golang.org>
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This change removes the ExecTracer2 experiment flag. This flag was
created as part of the tracer overhaul described in #60773.

Updates #66703
For #60773

Change-Id: Ib95b9dd8bb68b48e7543c4d28d853c6a518438f6
Reviewed-on: https://go-review.googlesource.com/c/go/+/576258
Auto-Submit: Carlos Amedee <carlos@golang.org>
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