It was reported that dm-crypt performs badly when the system is loaded[1]. So I'm adding an option "high_priority" that sets the workqueues and the write_thread to nice level -20. This used to be default in the past, but it caused audio skipping, so it had to be reverted - see the commit f612b2132db529feac4f965f28a1b9258ea7c22b. This commit makes it optional, so that normal users won't be harmed by it. [1] https://listman.redhat.com/archives/dm-devel/2023-February/053410.html Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> --- Documentation/admin-guide/device-mapper/dm-crypt.rst | 5 +++ drivers/md/dm-crypt.c | 28 +++++++++++++------ 2 files changed, 25 insertions(+), 8 deletions(-) Index: linux-2.6/drivers/md/dm-crypt.c =================================================================== --- linux-2.6.orig/drivers/md/dm-crypt.c 2024-04-08 19:54:41.000000000 +0200 +++ linux-2.6/drivers/md/dm-crypt.c 2024-04-08 19:54:58.000000000 +0200 @@ -137,9 +137,9 @@ struct iv_elephant_private { * and encrypts / decrypts at the same time. */ enum flags { DM_CRYPT_SUSPENDED, DM_CRYPT_KEY_VALID, - DM_CRYPT_SAME_CPU, DM_CRYPT_NO_OFFLOAD, - DM_CRYPT_NO_READ_WORKQUEUE, DM_CRYPT_NO_WRITE_WORKQUEUE, - DM_CRYPT_WRITE_INLINE }; + DM_CRYPT_SAME_CPU, DM_CRYPT_HIGH_PRIORITY, + DM_CRYPT_NO_OFFLOAD, DM_CRYPT_NO_READ_WORKQUEUE, + DM_CRYPT_NO_WRITE_WORKQUEUE, DM_CRYPT_WRITE_INLINE }; enum cipher_flags { CRYPT_MODE_INTEGRITY_AEAD, /* Use authenticated mode for cipher */ @@ -3134,7 +3134,7 @@ static int crypt_ctr_optional(struct dm_ struct crypt_config *cc = ti->private; struct dm_arg_set as; static const struct dm_arg _args[] = { - {0, 8, "Invalid number of feature args"}, + {0, 9, "Invalid number of feature args"}, }; unsigned int opt_params, val; const char *opt_string, *sval; @@ -3161,6 +3161,8 @@ static int crypt_ctr_optional(struct dm_ else if (!strcasecmp(opt_string, "same_cpu_crypt")) set_bit(DM_CRYPT_SAME_CPU, &cc->flags); + else if (!strcasecmp(opt_string, "high_priority")) + set_bit(DM_CRYPT_HIGH_PRIORITY, &cc->flags); else if (!strcasecmp(opt_string, "submit_from_crypt_cpus")) set_bit(DM_CRYPT_NO_OFFLOAD, &cc->flags); @@ -3399,18 +3401,22 @@ static int crypt_ctr(struct dm_target *t } ret = -ENOMEM; - cc->io_queue = alloc_workqueue("kcryptd_io/%s", WQ_MEM_RECLAIM, 1, devname); + cc->io_queue = alloc_workqueue("kcryptd_io/%s", WQ_MEM_RECLAIM | + test_bit(DM_CRYPT_HIGH_PRIORITY, &cc->flags) * WQ_HIGHPRI, + 1, devname); if (!cc->io_queue) { ti->error = "Couldn't create kcryptd io queue"; goto bad; } if (test_bit(DM_CRYPT_SAME_CPU, &cc->flags)) - cc->crypt_queue = alloc_workqueue("kcryptd/%s", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM, + cc->crypt_queue = alloc_workqueue("kcryptd/%s", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM | + test_bit(DM_CRYPT_HIGH_PRIORITY, &cc->flags) * WQ_HIGHPRI, 1, devname); else cc->crypt_queue = alloc_workqueue("kcryptd/%s", - WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM | WQ_UNBOUND, + WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM | WQ_UNBOUND | + test_bit(DM_CRYPT_HIGH_PRIORITY, &cc->flags) * WQ_HIGHPRI, num_online_cpus(), devname); if (!cc->crypt_queue) { ti->error = "Couldn't create kcryptd queue"; @@ -3427,6 +3433,8 @@ static int crypt_ctr(struct dm_target *t ti->error = "Couldn't spawn write thread"; goto bad; } + if (test_bit(DM_CRYPT_HIGH_PRIORITY, &cc->flags)) + set_user_nice(cc->write_thread, MIN_NICE); ti->num_flush_bios = 1; ti->limit_swap_bios = true; @@ -3547,6 +3555,7 @@ static void crypt_status(struct dm_targe 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_HIGH_PRIORITY, &cc->flags); num_feature_args += test_bit(DM_CRYPT_NO_OFFLOAD, &cc->flags); num_feature_args += test_bit(DM_CRYPT_NO_READ_WORKQUEUE, &cc->flags); num_feature_args += test_bit(DM_CRYPT_NO_WRITE_WORKQUEUE, &cc->flags); @@ -3560,6 +3569,8 @@ static void crypt_status(struct dm_targe DMEMIT(" allow_discards"); if (test_bit(DM_CRYPT_SAME_CPU, &cc->flags)) DMEMIT(" same_cpu_crypt"); + if (test_bit(DM_CRYPT_HIGH_PRIORITY, &cc->flags)) + DMEMIT(" high_priority"); if (test_bit(DM_CRYPT_NO_OFFLOAD, &cc->flags)) DMEMIT(" submit_from_crypt_cpus"); if (test_bit(DM_CRYPT_NO_READ_WORKQUEUE, &cc->flags)) @@ -3579,6 +3590,7 @@ static void crypt_status(struct dm_targe DMEMIT_TARGET_NAME_VERSION(ti->type); DMEMIT(",allow_discards=%c", ti->num_discard_bios ? 'y' : 'n'); DMEMIT(",same_cpu_crypt=%c", test_bit(DM_CRYPT_SAME_CPU, &cc->flags) ? 'y' : 'n'); + DMEMIT(",high_priority=%c", test_bit(DM_CRYPT_HIGH_PRIORITY, &cc->flags) ? 'y' : 'n'); DMEMIT(",submit_from_crypt_cpus=%c", test_bit(DM_CRYPT_NO_OFFLOAD, &cc->flags) ? 'y' : 'n'); DMEMIT(",no_read_workqueue=%c", test_bit(DM_CRYPT_NO_READ_WORKQUEUE, &cc->flags) ? @@ -3706,7 +3718,7 @@ static void crypt_io_hints(struct dm_tar static struct target_type crypt_target = { .name = "crypt", - .version = {1, 25, 0}, + .version = {1, 26, 0}, .module = THIS_MODULE, .ctr = crypt_ctr, .dtr = crypt_dtr, Index: linux-2.6/Documentation/admin-guide/device-mapper/dm-crypt.rst =================================================================== --- linux-2.6.orig/Documentation/admin-guide/device-mapper/dm-crypt.rst 2024-04-08 19:54:41.000000000 +0200 +++ linux-2.6/Documentation/admin-guide/device-mapper/dm-crypt.rst 2024-04-08 19:54:41.000000000 +0200 @@ -113,6 +113,11 @@ same_cpu_crypt The default is to use an unbound workqueue so that encryption work is automatically balanced between available CPUs. +high_priority + Set dm-crypt workqueues and the writer thread to high priority. This + improves throughput and latency of dm-crypt while degrading general + responsiveness of the system. + submit_from_crypt_cpus Disable offloading writes to a separate thread after encryption. There are some situations where offloading write bios from the
