From 0f5d8e6ee758f7023e4353cca75d785b2d4f6abe Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Fri, 13 Feb 2015 08:27:08 -0500 Subject: 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 Signed-off-by: Mike Snitzer --- Documentation/device-mapper/dm-crypt.txt | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'Documentation/device-mapper') 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: \ 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 -- cgit v1.2.3