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Scheduler should change pid+tid values to ensure unique in core-sharded-on-disk mixes #7401

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derekbruening opened this issue Mar 26, 2025 · 1 comment · Fixed by #7402
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Scheduler should change pid+tid values to ensure unique in core-sharded-on-disk mixes #7401

derekbruening opened this issue Mar 26, 2025 · 1 comment · Fixed by #7402
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@derekbruening
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For dynamic scheduling, the scheduler API allows easy identification of different workloads and threads within them, even when the same trace is included multiple times. But when we write out a core-sharded-on-disk trace and then read it in, that API no longer helps as it sees just one input. The pid and tid fields can be used to distinguish the interleaved original workloads and their threads, but those can collide, especially if one workload is included multiple times. We should have the scheduler replace the original pid and tid values to ensure uniqueness.

This would also help with analyzers that are currently using the pid/tid fields: we wouldn't have to migrate them to use the scheduler's input workload identifiers.

The proposal is to stick the workload ordinal in the upper 32 bits of the tid and pid. On Mac a thread is 64-bits already; we probably will just live with potential problems there for now.
@derekbruening derekbruening self-assigned this Mar 26, 2025
@derekbruening
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We also won't support 32-bit builds with record_filter where there are only 32 bits to hold the tid/pid. (Long-term probably 32-bit should use the 64-bit on-disk format as it has timestamp issues as well.)

derekbruening added a commit that referenced this issue Mar 27, 2025
@derekbruening
i#7401: Ensure unique pid,tid in drmemtrace schedules
73bc390 
In dynamic drmemtrace schedules combining multiple workloads, there
can be pid or tid collisions.  We solve that by having the scheduler
set the workload ordinal in the top 32 bits of both the pid and tid.
We ignore tids being 64-bit values on Mac; and we do not support
unique values for 32-bit builds when trace_entry_t-based tools such as
record_filter are used.

Documents this, along with missing docs for cpuid and timestamp
modifications.

Updates the view tool and schedule stats to print tids in hex, to make
it easier to distinguish the workload ordinal.  Updates test templates
and docs for this change.

Adds scheduler unit tests.

Here is what this looks like:
===========================================================================
$ bin64/drrun -t drmemtrace -tool view -multi_indir ../src/clients/drcachesim/tests/drmemtrace.threadsig.x64.tracedir:../src/clients/drcachesim/tests/drmemtrace.threadsig.x64.tracedir -core_sharded -cores 1 -sched_quantum 10 2>&1 | less
Output format:
<--record#-> <--instr#->: <---tid---> <record details>
------------------------------------------------------------
           1           0:       d51be <marker: version 7>
           2           0:       d51be <marker: filetype 0xe40>
           3           0:       d51be <marker: cache line size 64>
...
------------------------------------------------------------
         135          60:   1000d51be <marker: version 7>
         136          60:   1000d51be <marker: filetype 0xe40>
         137          60:   1000d51be <marker: cache line size 64>
===========================================================================

Fixes #7401
This was referenced Mar 27, 2025
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derekbruening added a commit that referenced this issue Mar 28, 2025
@derekbruening
i#7401: Ensure unique pid,tid in drmemtrace schedules (#7402)
069cbaf 
In dynamic drmemtrace schedules combining multiple workloads, there can
be pid or tid collisions. We solve that by having the scheduler set the
workload ordinal in the top 32 bits of both the pid and tid. We ignore
tids being 64-bit values on Mac; and we do not support unique values for
32-bit builds when trace_entry_t-based tools such as record_filter are
used.

Documents this, along with missing docs for cpuid and timestamp
modifications.

Updates the view tool and schedule stats to print tids in hex, to make
it easier to distinguish the workload ordinal. Updates test templates
and docs for this change.

Adds scheduler unit tests.

Here is what this looks like:
```
drmemtrace -tool view -multi_indir ../src/clients/drcachesim/tests/drmemtrace.threadsig.x64.tracedir:../src/clients/drcachesim/tests/drmemtrace.threadsig.x64.tracedir -core_sharded -cores 1 -sched_quantum 10 2>&1 | less Output format:
<--record#-> <--instr#->: <---tid---> <record details>
------------------------------------------------------------
           1           0:       d51be <marker: version 7>
           2           0:       d51be <marker: filetype 0xe40>
           3           0:       d51be <marker: cache line size 64>
...
------------------------------------------------------------
         135          60:   1000d51be <marker: version 7>
         136          60:   1000d51be <marker: filetype 0xe40>
         137          60:   1000d51be <marker: cache line size 64>
```

Fixes #7401
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i#7401: Ensure unique pid,tid in drmemtrace schedules DynamoRIO/dynamorio
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