Intern repository mapping entries#19269
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All repositories generated by a module extension have the same repository mapping entries. Without interning, if a module extension generates N repositories, each such repository would have its own copy with (more than) N entries, resulting in memory usage that is quadratic in N. We intern the entries, not the RepositoryMapping itself, because the latter also includes the owner repo, which differs between extension repos. Output of `bazel info used-heap-size-after-gc` after running a build with a synthetic module extension generating N + 1 repos: before N=100: 32MB N=1000: 77MB N=3000: 371MB N=5000: 961MB N=10000: 3614MB after N=100: 32MB N=1000: 44MB N=3000: 71MB N=5000: 91MB N=10000: 158MB
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Wyverald
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Aug 17, 2023
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nice, thank you for the investigation and prompt fix!
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@bazel-io fork 6.4.0 |
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@fmeum I accidentally clicked on "Update branch" button, causing a merge commit to be made. Can you please reset to the original commit? My apologies. cc: @bazelbuild/triage |
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@iancha1992 I think you are still able to import the PR, you can fix the GIT_AUTHORS manually, I can help review ;) |
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All repositories generated by a module extension have the same repository mapping entries. Without interning, if a module extension generates N repositories, each such repository would have its own copy with (more than) N entries, resulting in overall memory usage quadratic in N. We intern the entries, not the `RepositoryMapping` itself, since the latter also includes the owner repo, which differs between extension repos. Output of `bazel info used-heap-size-after-gc` after running a build with a synthetic module extension generating N + 1 repos and requesting all of them: ``` before N=100: 32MB N=1000: 77MB N=3000: 371MB N=5000: 961MB N=10000: 3614MB after N=100: 32MB N=1000: 44MB N=3000: 71MB N=5000: 91MB N=10000: 158MB ``` Closes bazelbuild#19269. PiperOrigin-RevId: 558940840 Change-Id: I07402f203b5f11bf448a1ae9e9ee4637ad4c536d
iancha1992
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All repositories generated by a module extension have the same repository mapping entries. Without interning, if a module extension generates N repositories, each such repository would have its own copy with (more than) N entries, resulting in overall memory usage quadratic in N. We intern the entries, not the `RepositoryMapping` itself, since the latter also includes the owner repo, which differs between extension repos. Output of `bazel info used-heap-size-after-gc` after running a build with a synthetic module extension generating N + 1 repos and requesting all of them: ``` before N=100: 32MB N=1000: 77MB N=3000: 371MB N=5000: 961MB N=10000: 3614MB after N=100: 32MB N=1000: 44MB N=3000: 71MB N=5000: 91MB N=10000: 158MB ``` Closes #19269. Commit 74aadb2 PiperOrigin-RevId: 558940840 Change-Id: I07402f203b5f11bf448a1ae9e9ee4637ad4c536d Co-authored-by: Fabian Meumertzheim <fabian@meumertzhe.im>
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The changes in this PR have been included in Bazel 6.4.0 RC1. Please test out the release candidate and report any issues as soon as possible. If you're using Bazelisk, you can point to the latest RC by setting USE_BAZEL_VERSION=last_rc. |
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All repositories generated by a module extension have the same repository mapping entries. Without interning, if a module extension generates N repositories, each such repository would have its own copy with (more than) N entries, resulting in overall memory usage quadratic in N.
We intern the entries, not the
RepositoryMappingitself, since the latter also includes the owner repo, which differs between extension repos.Output of
bazel info used-heap-size-after-gcafter running a build with a synthetic module extension generating N + 1 repos and requesting all of them: