在 2023/2/28 2:06, Mike Snitzer 写道:
On Mon, Feb 27 2023 at 1:03P -0500,
Mike Snitzer <snitzer@xxxxxxxxxx> wrote:
On Mon, Feb 27 2023 at 12:55P -0500,
Mike Snitzer <snitzer@xxxxxxxxxx> wrote:
On Sun, Feb 26 2023 at 8:31P -0500,
yangerkun <yangerkun@xxxxxxxxxxxxxxx> wrote:
在 2023/2/26 10:01, Bart Van Assche 写道:
On 2/22/23 19:19, yangerkun wrote:
@@ -1924,6 +1926,10 @@ static int dmcrypt_write(void *data)
BUG_ON(rb_parent(write_tree.rb_node));
+ if (time_is_before_jiffies(start_time + HZ)) {
+ schedule();
+ start_time = jiffies;
+ }
Why schedule() instead of cond_resched()?
cond_resched may not really schedule, which may trigger the problem too, but
it seems after 1 second, it may never happend?
I had the same question as Bart when reviewing your homegrown
conditional schedule(). Hopefully you can reproduce this issue? If
so, please see if simply using cond_resched() fixes the issue.
This seems like a more appropriate patch:
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 87c5706131f2..faba1be572f9 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -1937,6 +1937,7 @@ static int dmcrypt_write(void *data)
io = crypt_io_from_node(rb_first(&write_tree));
rb_erase(&io->rb_node, &write_tree);
kcryptd_io_write(io);
+ cond_resched();
} while (!RB_EMPTY_ROOT(&write_tree));
blk_finish_plug(&plug);
}
or:
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 87c5706131f2..3ba2fd3e4358 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -1934,6 +1934,7 @@ static int dmcrypt_write(void *data)
*/
blk_start_plug(&plug);
do {
+ cond_resched();
io = crypt_io_from_node(rb_first(&write_tree));
rb_erase(&io->rb_node, &write_tree);
kcryptd_io_write(io);
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.
kcryptd_crypt_write_io_submit will wakeup write_thread once there is a
empty write_tree, and dmcrypt_write will peel the old write_tree to
submit bio, so there can not exist too many bio in write_tree. Then I
choose yield cpu before the 'while' that submit bio...
Thanks,
Kun.
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