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authorMikulas Patocka <mpatocka@redhat.com>2015-02-13 16:27:08 +0300
committerMike Snitzer <snitzer@redhat.com>2015-02-16 19:11:15 +0300
commit0f5d8e6ee758f7023e4353cca75d785b2d4f6abe (patch)
tree836041a22c3b5f5eb6151f27b7b0dec1714ac5fd /Documentation
parentdc2676210c425ee8e5cb1bec5bc84d004ddf4179 (diff)
downloadlinux-0f5d8e6ee758f7023e4353cca75d785b2d4f6abe.tar.xz
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.txt10
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