70 lines
2.6 KiB
Python
70 lines
2.6 KiB
Python
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#!/usr/bin/env python
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"""Hand the archive's file handles back to the host.
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The archive is on a virtiofs share whose daemon holds a host file descriptor per
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inode the guest has looked up. Anything that reads a lot of the archive leaves those
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inodes cached, and the handles with them, until something forces the guest to evict
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them -- at which point the daemon can run out and the mount starts refusing *every*
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open, which surfaces across the whole machine as "too many open files in system".
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The pipeline's own bulk jobs now reclaim as they go and again when they finish, so
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this should rarely be needed. It exists for when something else has loaded the cache,
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or to check where things stand:
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reclaim.py # report, then reclaim if needed
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reclaim.py --check # report only, change nothing
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sudo reclaim.py # uses drop_caches: instant, and far gentler
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Without root the only lever available is memory pressure, which means briefly
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allocating several GiB. Running under sudo avoids that entirely.
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"""
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import argparse
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import os
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import sys
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sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
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from suvi import vfs
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#: Roughly the slab size at which the daemon is likely near a 1M descriptor limit.
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#: A cached dentry plus inode is on the order of a kilobyte, so a gigabyte of
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#: reclaimable slab is on the order of a million inodes.
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CONCERN_GIB = 1.0
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def report(prefix):
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slab = vfs.reclaimable_kb() / (1024 * 1024)
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print(f"{prefix:>8}: {slab:.2f} GiB reclaimable slab "
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f"(~{slab:.1f}M cached inodes), {vfs.available_gib():.1f} GiB available")
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return slab
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def main(argv=None):
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parser = argparse.ArgumentParser(description=__doc__,
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formatter_class=argparse.RawDescriptionHelpFormatter)
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parser.add_argument("--check", action="store_true", help="report only, reclaim nothing")
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parser.add_argument("--force", action="store_true", help="reclaim even if it looks fine")
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args = parser.parse_args(argv)
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before = report("before")
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if args.check:
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print(" (check only; nothing reclaimed)")
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return 0 if before < CONCERN_GIB else 1
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if before < CONCERN_GIB and not args.force:
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print(f" below {CONCERN_GIB} GiB; nothing to do. Use --force to reclaim anyway.")
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return 0
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if os.geteuid() != 0:
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print(" not root, so using memory pressure; run under sudo for the direct path")
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freed = vfs.release_handles()
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after = report("after")
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print(f" {'reclaimed' if freed else 'no change'}: "
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f"{before - after:+.2f} GiB")
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return 0
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if __name__ == "__main__":
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sys.exit(main())
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