Hey Milan, Hope things are good for you! On Tue, Apr 09 2024 at 9:04P -0400, Milan Broz <gmazyland@xxxxxxxxx> wrote: > On 4/8/24 9:36 PM, Mikulas Patocka wrote: > > 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 > > It is pity that we need an optional flag here leaving decision to the user > (I would prefer a magic workqueue setting that will self-tune automagically.) > > I guess people will set it and forgot about it (until some problem reappears) > - as we can store persistent performance flags for LUKS2, so this one will > be a new option there. > > ... > > > @@ -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); > > Just one nitpicking though: > > test_bit(...) ? WQ_HIGHPRI : 0 > > looks more clear/readable to me (but I guess test_bit should always return 0/1 only). I agree, but I actually cleaned stuff up in further with the following incremental patch: diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c index fad4b920008f..eabc576d8d28 100644 --- a/drivers/md/dm-crypt.c +++ b/drivers/md/dm-crypt.c @@ -3234,6 +3234,7 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv) const char *devname = dm_table_device_name(ti->table); int key_size; unsigned int align_mask; + unsigned int common_wq_flags; unsigned long long tmpll; int ret; size_t iv_size_padding, additional_req_size; @@ -3401,23 +3402,25 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv) } ret = -ENOMEM; - cc->io_queue = alloc_workqueue("kcryptd_io/%s", WQ_MEM_RECLAIM | - test_bit(DM_CRYPT_HIGH_PRIORITY, &cc->flags) * WQ_HIGHPRI, - 1, devname); + common_wq_flags = WQ_MEM_RECLAIM; + if (test_bit(DM_CRYPT_HIGH_PRIORITY, &cc->flags)) + common_wq_flags |= WQ_HIGHPRI; + + cc->io_queue = alloc_workqueue("kcryptd_io/%s", common_wq_flags, 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 | - test_bit(DM_CRYPT_HIGH_PRIORITY, &cc->flags) * WQ_HIGHPRI, + if (test_bit(DM_CRYPT_SAME_CPU, &cc->flags)) { + cc->crypt_queue = alloc_workqueue("kcryptd/%s", + common_wq_flags | WQ_CPU_INTENSIVE, 1, devname); - else + } else { cc->crypt_queue = alloc_workqueue("kcryptd/%s", - WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM | WQ_UNBOUND | - test_bit(DM_CRYPT_HIGH_PRIORITY, &cc->flags) * WQ_HIGHPRI, + common_wq_flags | WQ_CPU_INTENSIVE | WQ_UNBOUND, num_online_cpus(), devname); + } if (!cc->crypt_queue) { ti->error = "Couldn't create kcryptd queue"; goto bad; The end result is here (also revised commit header): https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-6.10&id=fdca2c9cb999e781fbb3171541c709bf0e43fbda Doing it this way made sense given the following commit I staged (to reintroduce the use of WQ_SYSFS, will send mail on that next). Thanks, Mike
