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| author | Mikulas Patocka <mpatocka@redhat.com> | 2015-02-13 08:27:08 -0500 |
|---|---|---|
| committer | Mike Snitzer <snitzer@redhat.com> | 2015-02-16 11:11:15 -0500 |
| commit | 0f5d8e6ee758f7023e4353cca75d785b2d4f6abe (patch) | |
| tree | 836041a22c3b5f5eb6151f27b7b0dec1714ac5fd /Documentation | |
| parent | dc2676210c425ee8e5cb1bec5bc84d004ddf4179 (diff) | |
| download | lwn-0f5d8e6ee758f7023e4353cca75d785b2d4f6abe.tar.gz lwn-0f5d8e6ee758f7023e4353cca75d785b2d4f6abe.zip | |
dm crypt: add 'submit_from_crypt_cpus' option
Make it possible to disable offloading writes by setting the optional
'submit_from_crypt_cpus' table argument.
There are some situations where offloading write bios from the
encryption threads to a single thread degrades performance
significantly.
The default is to offload write bios to the same thread because it
benefits CFQ to have writes submitted using the same IO context.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/device-mapper/dm-crypt.txt | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/Documentation/device-mapper/dm-crypt.txt b/Documentation/device-mapper/dm-crypt.txt index 571f24ffc91c..ad697781f9ac 100644 --- a/Documentation/device-mapper/dm-crypt.txt +++ b/Documentation/device-mapper/dm-crypt.txt @@ -51,7 +51,7 @@ Parameters: <cipher> <key> <iv_offset> <device path> \ Otherwise #opt_params is the number of following arguments. Example of optional parameters section: - 2 allow_discards same_cpu_crypt + 3 allow_discards same_cpu_crypt submit_from_crypt_cpus allow_discards Block discard requests (a.k.a. TRIM) are passed through the crypt device. @@ -68,6 +68,14 @@ same_cpu_crypt The default is to use an unbound workqueue so that encryption work is automatically balanced between available CPUs. +submit_from_crypt_cpus + Disable offloading writes to a separate thread after encryption. + There are some situations where offloading write bios from the + encryption threads to a single thread degrades performance + significantly. The default is to offload write bios to the same + thread because it benefits CFQ to have writes submitted using the + same context. + Example scripts =============== LUKS (Linux Unified Key Setup) is now the preferred way to set up disk |