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Remove --no-write-protect-code-memory #822

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Oct 22, 2025
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Remove --no-write-protect-code-memory #822

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7 changes: 2 additions & 5 deletions src/docs/linux-perf.md
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Original file line number Diff line number Diff line change
Expand Up @@ -96,8 +96,7 @@ This requires a two-step process, first `perf record` creates a `perf.data` file
perf record --call-graph=fp --clockid=mono --freq=max \
--output=perf.data
out/x64.release/d8 \
--perf-prof --no-write-protect-code-memory \
--interpreted-frames-native-stack \
--perf-prof --interpreted-frames-native-stack \
test.js;
perf inject --jit --input=perf.data --output=perf.data.jitted;
perf report --input=perf.data.jitted;
Expand All @@ -107,8 +106,6 @@ perf report --input=perf.data.jitted;

[`--perf-prof`](https://source.chromium.org/search?q=FLAG_perf_prof) is used to the V8 command-line to record performance samples in JIT code.

[`--nowrite-protect-code-memory`](https://source.chromium.org/search?q=FLAG_nowrite_protect_code_memory) is required to disable write protection for code memory. This is necessary because `perf` discards information about code pages when it sees the event corresponding to removing the write bit from the code page. Here’s an example that records samples from a test JavaScript file:

[`--interpreted-frames-native-stack`](https://source.chromium.org/search?q=FLAG_interpreted_frames_native_stack) is used to create different entry points (copied versions of InterpreterEntryTrampoline) for interpreted functions so they can be distinguished by `perf` based on the address alone. Since the InterpreterEntryTrampoline has to be copied this comes at slight performance and memory regression.


Expand All @@ -122,7 +119,7 @@ perf report --input=perf.data.jitted;
out/x64.release/chrome \
--user-data-dir=`mktemp -d` \
--no-sandbox --incognito --enable-benchmarking \
--js-flags='--perf-prof --no-write-protect-code-memory --interpreted-frames-native-stack'
--js-flags='--perf-prof --interpreted-frames-native-stack'
```

1. After starting up chrome, find the renderer process id using the Task Manager and use it to start profiling:
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