Avoid using unnecessary udev.settle calls #897
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Conan-Kudo
approved these changes
Sep 10, 2020
vpodzime
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Sep 10, 2020
udev.resolve_devspec is slow and uses udev.settle, we should avoid using it if possible when getting system mountpoints.
We currently run udev.settle for every _pre_teardown call even if there is no change or format teardown. This commit moves the udev.settle call to format classes so it is called only when format.teardown calls in _pre_teardown change the format.
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dwlehman
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Sep 14, 2020
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You could also set a flag based on the initial status of the format and then conditionally call settle only when the flag indicates that the format was initially active. It would change less, but I'm not sure if it's actually better. It's probably a good thing to explicitly call settle every time we tear down a format, whether that's done in DeviceFormat.teardown or in the subclasses as you've done.
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Apparently it is completely normal to have hundreds of btrfs snapshots and blivet is currently not very good in handling this situation.
resetis relatively fast, butteardown_all(which anaconda runs multiple times during installation) can take more than 10 minutes on systems with 500 snapshots (rhbz#1876162).I was able to find two issues in our code:
MountsCacheusesudev.resolve_devicefor every mountpoint query.resolve_deviceitself usesudev.settleand also iterates over all devices in the UDev database.StorageDevice._pre_teardownalways runsudev.settleeven when theteardownis no-op. This means we runudev.settle3 times for every snapshot duringteardown_all.