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dm crypt: offload writes to thread · torvalds/linux@dc26762 · GitHub

 4 years ago
source link: https://github.com/torvalds/linux/commit/dc2676210c425ee8e5cb1bec5bc84d004ddf4179
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offload writes to thread · torvalds/linux@dc26762 · GitHubPermalink

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dm crypt: offload writes to thread 

Submitting write bios directly in the encryption thread caused serious
performance degradation.  On a multiprocessor machine, encryption requests
finish in a different order than they were submitted.  Consequently, write
requests would be submitted in a different order and it could cause severe
performance degradation.

Move the submission of write requests to a separate thread so that the
requests can be sorted before submitting.  But this commit improves
dm-crypt performance even without having dm-crypt perform request
sorting (in particular it enables IO schedulers like CFQ to sort more
effectively).

Note: it is required that a previous commit ("dm crypt: don't allocate
pages for a partial request") be applied before applying this patch.
Otherwise, this commit could introduce a crash.

Signed-off-by: Mikulas Patocka <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>

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