mirror of https://github.com/postgres/postgres
There previously were a number of issues: - We'd upload the cache even if we already had a high hit rate. That means we churn through the available cache space very quickly. For this we now check if the cache hit ratio is already high, and skip uploading a new cache in that case. - We'd generate per-branch caches, even if master's already would suffice, because the branch doesn't change much This is solved indirectly by the above. - The cache key allowed prefix matches based on the branch, e.g. master-pending would always use master's branch Replace the cache key element separator of - with :, which is not a valid part of a branch name. - When rebasing a feature branch, we'd start with just that branch's cache, rather than also having the newer cache of master available This is solved by downloading by master's and the feature branch's cache, simply overlaying both. That's possible because ccache is content addressed. - The size of a cache would increase to the max, even though there likely will be no benefit from old cache entries. Address this by explicitly evicting old data and also recompressing the cache before uploading it. In my testing this utilizes the available cache space (10GB for personal accounts) much more effectively than before. The not entirely trivial determination of whether it's worth uploading a cache entry is moved to a python script. I first had it as shell, but that gets awkward. This way it'd also be more viable to use ccache for msvc at some point. The per-job redundancies are a bit annoying. There's a way around that, by using composite actions, but I think that might be harder to understand, without all that much of an improvement. Reviewed-by: Nazir Bilal Yavuz <byavuz81@gmail.com> Discussion: https://postgr.es/m/7eugqon2ilnaq6yimtq7prtl5wlia43mhpmwlydzlw4u4wonaz@hh2fagz5bjuumaster
Andres Freund
3 days ago
parent
4b1e18b057
commit
f52c44ce48
@ -0,0 +1,104 @@ |
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#!/usr/bin/env python3 |
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|
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import os |
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import re |
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import shutil |
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import subprocess |
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|
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def run(cmd, check=True): |
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return subprocess.run( |
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cmd, |
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check=check, |
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text=True, |
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stdout=subprocess.PIPE, |
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stderr=subprocess.STDOUT, |
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).stdout |
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|
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def parse_ccache_stats(): |
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out = run(["ccache", "--print-stats"]) |
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hits = 0 |
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misses = 0 |
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|
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for line in out.splitlines(): |
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line = line.strip() |
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m = re.match(r"^local_storage_hit\s+(\d+)$", line) |
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if m: |
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hits = int(m.group(1)) |
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continue |
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m = re.match(r"^local_storage_miss\s+(\d+)$", line) |
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if m: |
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misses = int(m.group(1)) |
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continue |
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|
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return hits, misses |
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|
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def append_github_output(key, value): |
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output_path = os.environ["GITHUB_OUTPUT"] |
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with open(output_path, "a", encoding="utf-8") as f: |
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f.write(f"{key}={value}\n") |
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|
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def main(): |
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on_default_branch = os.environ["ON_DEFAULT_BRANCH"] == "true" |
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# Decide the target hit percentage below which we decide to upload a new |
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# cache. On non-default branches a few misses aren't that bad. But, as the |
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# caches of the default branch are shared with all branches, it's worth |
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# aiming for a higher ratio there. |
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target_rate = 95 if on_default_branch else 80 |
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|
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# Log ccache stats, useful for more in-depth understanding. To avoid |
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# swamping the output, collapse it in a group. |
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print("::group::ccache_stats") |
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print(run(["ccache", "-s", "-vv"])) |
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print("::endgroup::") |
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|
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# compute cache hit ratio |
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hits, misses = parse_ccache_stats() |
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total = hits + misses |
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hit_pct = int((hits / total) * 100) if total > 0 else 100 |
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print(f"hits: {hits}, misses: {misses}, hit_pct: {hit_pct}, target rate: {target_rate}") |
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# If the cache hit ratio was high, or the absolute number of misses |
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# (e.g. in case of a failed build) was low, there is no point in |
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# generating a new cache entry. We have limited cache space. |
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if hit_pct >= target_rate: |
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print(f"hit rate {hit_pct} is above target of {target_rate}, skip creating new cache entry") |
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should_save = False |
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elif misses <= 10: |
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print(f"only {misses} misses, skip creating new cache entry") |
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should_save = False |
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else: |
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print(f"hit rate {hit_pct} is below target of {target_rate}, create new cache entry") |
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should_save = True |
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append_github_output("should_save", str(should_save).lower()) |
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if not should_save: |
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return 0 |
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# It's not worth persisting old cache entries (e.g. from before a |
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# change to a central header, or from the default branch if this |
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# branch differs a lot). Therefore evict ccache entries that are a |
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# bit older. The cutoff here is fairly arbitrary, it could |
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# probably be improved. |
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print("::group::ccache_shrink") |
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print(run(["ccache", "--evict-older-than", f"{45*60}s"])) |
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print(run(["ccache", "-X", "10"])) |
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# Don't store ccache stats, otherwise we'd need to reset the cache access |
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# data after restoring the cache in the next run, to be able to get the |
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# hit ratio of the CI run. |
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print(run(["ccache", "-z"])) |
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print("::endgroup::") |
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# Before continuing, try to kill all ccache instances, otherwise |
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# it's possible that on cancellations there is still running |
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# ccaches that cause the upload to fail. |
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if shutil.which("killall"): |
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print(run(["killall", "ccache"], check=False)) |
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return 0 |
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if __name__ == "__main__": |
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exit(main()) |
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