pid: use PROT_READ/MAP_SHARED for readonly maps
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Authored by seirl on Jul 23 2020, 12:22 PM.

Details

Reviewers

olasd
zack

Maniphest Tasks

T2492: swh-graph: loading maps fail when available memory is too low: Cannot allocate memory

Commits

rDGRPH39430074227c: pid: use PROT_READ/MAP_SHARED for readonly maps

Summary

We used to have PROT_READ | PROT_WRITE and MAP_PRIVATE for readonly
maps. However, this would reserve copy-on-write space and make the
service OOM. We could also use MAP_NORESERVE to avoid committing for
that much memory in advance, but we really don't need to have writable
space at all, so we just set the prot flags properly.

Fix T2492

Test Plan

tested in prod

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Unit

Automatic diff as part of commit; unit tests not applicable.

Event Timeline

seirl created this revision.Jul 23 2020, 12:22 PM

zack resigned from this revision.Jul 23 2020, 12:23 PM

Thanks!

This revision is now accepted and ready to land.Jul 23 2020, 12:23 PM

Build is green

Patch application report for D3599 (id=12678)

Rebasing onto 481fcc9fc0...

Current branch diff-target is up to date.

Changes applied before test

commit 39430074227cf35d51eeccfde8e151c0aa1e257a
Author: Antoine Pietri <antoine.pietri1@gmail.com>
Date:   Thu Jul 23 12:17:18 2020 +0200

    pid: use PROT_READ/MAP_SHARED for readonly maps
    
    We used to have PROT_READ | PROT_WRITE and MAP_PRIVATE for readonly
    maps. However, this would reserve copy-on-write space and make the
    service OOM. We could also use MAP_NORESERVE to avoid committing for
    that much memory in advance, but we really don't need to have writable
    space at all, so we just set the prot flags properly.
    
    Fix T2492

See https://jenkins.softwareheritage.org/job/DGRPH/job/tests-on-diff/10/ for more details.

Harbormaster completed remote builds in B13903: Diff 12678.Jul 23 2020, 12:24 PM

Closed by commit rDGRPH39430074227c: pid: use PROT_READ/MAP_SHARED for readonly maps (authored by seirl). · Explain WhyJul 23 2020, 12:32 PM

This revision was automatically updated to reflect the committed changes.

seirl added a commit: rDGRPH39430074227c: pid: use PROT_READ/MAP_SHARED for readonly maps.