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authorMikulas Patocka <mpatocka@redhat.com>2015-02-13 08:25:59 -0500
committerMike Snitzer <snitzer@redhat.com>2015-02-16 11:11:14 -0500
commitdc2676210c425ee8e5cb1bec5bc84d004ddf4179 (patch)
tree2d38e1d74895e7cf419a0408805ed73673d69425 /Documentation/device-mapper
parent94f5e0243c48aa01441c987743dc468e2d6eaca2 (diff)
downloadlinux-dc2676210c425ee8e5cb1bec5bc84d004ddf4179.tar.bz2
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 <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
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