On Mon, 6 Mar 2023, Mikulas Patocka wrote: > > Hi, > > > > Thanks a lot for your review! > > > > It's ok to fix the softlockup, but for async write encrypt, > > kcryptd_crypt_write_io_submit will add bio to write_tree, and once we > > call cond_resched before every kcryptd_io_write, the write performance > > may be poor while we meet a high cpu usage scene. > > Hi > > To fix this problem, find the PID of the process "dmcrypt_write" and > change its priority to -20, for example "renice -n -20 -p 34748". > > This is the proper way how to fix it; locking up the process for one > second is not. > > We used to have high-priority workqueues by default, but it caused audio > playback skipping, so we had to revert it - see > f612b2132db529feac4f965f28a1b9258ea7c22b. > > Perhaps we should add an option to have high-priority kernel threads? > > Mikulas Here I'm sending a patch that makes it optional to raise the priority of dm-crypt workqueues and the write thread. Test it, if it helps for you. Mikulas From: Mikulas Patocka <mpatocka@xxxxxxxxxx> 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 the 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 +++ linux-2.6/drivers/md/dm-crypt.c @@ -133,9 +133,9 @@ 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 */ @@ -3087,7 +3087,7 @@ 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; @@ -3114,6 +3114,8 @@ 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); @@ -3352,18 +3354,22 @@ 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"; @@ -3380,6 +3386,8 @@ 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; @@ -3500,6 +3508,7 @@ 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); @@ -3513,6 +3522,8 @@ 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)) @@ -3532,6 +3543,7 @@ 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) ? @@ -3659,7 +3671,7 @@ static void crypt_io_hints(struct dm_tar static struct target_type crypt_target = { .name = "crypt", - .version = {1, 24, 0}, + .version = {1, 25, 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 +++ linux-2.6/Documentation/admin-guide/device-mapper/dm-crypt.rst @@ -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 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel
