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authorMikulas Patocka <mpatocka@redhat.com>2015-02-13 08:27:08 -0500
committerAlex Shi <alex.shi@linaro.org>2015-06-24 11:40:02 +0800
commit36f43c352e9efea23e9bd47752b34e061c2504f5 (patch)
tree06464e729a8a109f092395450a50466842461705
parent9d4f07bc5998348afa5de3441c896cbec1dc83f5 (diff)
downloadlinux-linaro-stable-36f43c352e9efea23e9bd47752b34e061c2504f5.tar.gz
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> (cherry picked from commit 0f5d8e6ee758f7023e4353cca75d785b2d4f6abe) Signed-off-by: Alex Shi <alex.shi@linaro.org>
-rw-r--r--Documentation/device-mapper/dm-crypt.txt10
-rw-r--r--drivers/md/dm-crypt.c16
2 files changed, 23 insertions, 3 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
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index d216a99dabf7..d97f9eaa9145 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -110,7 +110,8 @@ struct iv_tcw_private {
* Crypt: maps a linear range of a block device
* and encrypts / decrypts at the same time.
*/
-enum flags { DM_CRYPT_SUSPENDED, DM_CRYPT_KEY_VALID, DM_CRYPT_SAME_CPU };
+enum flags { DM_CRYPT_SUSPENDED, DM_CRYPT_KEY_VALID,
+ DM_CRYPT_SAME_CPU, DM_CRYPT_NO_OFFLOAD };
/*
* The fields in here must be read only after initialization.
@@ -1245,6 +1246,11 @@ static void kcryptd_crypt_write_io_submit(struct dm_crypt_io *io, int async)
clone->bi_iter.bi_sector = cc->start + io->sector;
+ if (likely(!async) && test_bit(DM_CRYPT_NO_OFFLOAD, &cc->flags)) {
+ generic_make_request(clone);
+ return;
+ }
+
spin_lock_irqsave(&cc->write_thread_wait.lock, flags);
list_add_tail(&io->list, &cc->write_thread_list);
wake_up_locked(&cc->write_thread_wait);
@@ -1699,7 +1705,7 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
char dummy;
static struct dm_arg _args[] = {
- {0, 2, "Invalid number of feature args"},
+ {0, 3, "Invalid number of feature args"},
};
if (argc < 5) {
@@ -1807,6 +1813,9 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
else if (!strcasecmp(opt_string, "same_cpu_crypt"))
set_bit(DM_CRYPT_SAME_CPU, &cc->flags);
+ else if (!strcasecmp(opt_string, "submit_from_crypt_cpus"))
+ set_bit(DM_CRYPT_NO_OFFLOAD, &cc->flags);
+
else {
ti->error = "Invalid feature arguments";
goto bad;
@@ -1910,12 +1919,15 @@ static void crypt_status(struct dm_target *ti, status_type_t type,
num_feature_args += !!ti->num_discard_bios;
num_feature_args += test_bit(DM_CRYPT_SAME_CPU, &cc->flags);
+ num_feature_args += test_bit(DM_CRYPT_NO_OFFLOAD, &cc->flags);
if (num_feature_args) {
DMEMIT(" %d", num_feature_args);
if (ti->num_discard_bios)
DMEMIT(" allow_discards");
if (test_bit(DM_CRYPT_SAME_CPU, &cc->flags))
DMEMIT(" same_cpu_crypt");
+ if (test_bit(DM_CRYPT_NO_OFFLOAD, &cc->flags))
+ DMEMIT(" submit_from_crypt_cpus");
}
break;