FAQ Search Today's Posts Mark Forums Read
» Video Reviews

» Linux Archive

Linux-archive is a website aiming to archive linux email lists and to make them easily accessible for linux users/developers.


» Sponsor

» Partners

» Sponsor

Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
LinkBack Thread Tools
 
Old 08-21-2012, 09:09 AM
Mikulas Patocka
 
Default dm-crypt: offload writes to thread

Submitting write bios directly in the encryption thread caused serious
performance degradation. On multiprocessor machine encryption requests
finish in a different order than they were submitted in. Consequently, write
requests would be submitted in a different order and it could cause severe
performance degradation.

This patch moves submitting write requests to a separate thread so that
the requests can be sorted before submitting.

Sorting in implemented in the next patch.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
---
drivers/md/dm-crypt.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 80 insertions(+), 4 deletions(-)

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 9316630..0e31454 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -49,6 +49,8 @@ struct dm_crypt_io {

int error;
sector_t sector;
+
+ struct list_head list;
};

struct dm_crypt_request {
@@ -120,6 +122,10 @@ struct crypt_config {
wait_queue_head_t crypt_thread_wait;
struct list_head crypt_thread_list;

+ struct task_struct *write_thread;
+ wait_queue_head_t write_thread_wait;
+ struct list_head write_thread_list;
+
char *cipher;
char *cipher_string;

@@ -1069,9 +1075,8 @@ static int kcryptd_io_read(struct dm_crypt_io *io)
return 0;
}

-static void kcryptd_io_write(struct work_struct *work)
+static void kcryptd_io_write(struct dm_crypt_io *io)
{
- struct dm_crypt_io *io = container_of(work, struct dm_crypt_io, work);
struct crypt_config *cc = io->cc;
struct bio *clone = io->bio_out;

@@ -1087,12 +1092,68 @@ static void kcryptd_io_write(struct work_struct *work)
generic_make_request(clone);
}

+static int dmcrypt_write(void *data)
+{
+ struct crypt_config *cc = data;
+ while (1) {
+ struct list_head local_list;
+ struct blk_plug plug;
+
+ DECLARE_WAITQUEUE(wait, current);
+
+ spin_lock_irq(&cc->write_thread_wait.lock);
+continue_locked:
+
+ if (!list_empty(&cc->write_thread_list))
+ goto pop_from_list;
+
+ __set_current_state(TASK_INTERRUPTIBLE);
+ __add_wait_queue(&cc->write_thread_wait, &wait);
+
+ spin_unlock_irq(&cc->write_thread_wait.lock);
+
+ if (unlikely(kthread_should_stop())) {
+ set_task_state(current, TASK_RUNNING);
+ remove_wait_queue(&cc->write_thread_wait, &wait);
+ break;
+ }
+
+ schedule();
+
+ set_task_state(current, TASK_RUNNING);
+ spin_lock_irq(&cc->write_thread_wait.lock);
+ __remove_wait_queue(&cc->write_thread_wait, &wait);
+ goto continue_locked;
+
+pop_from_list:
+ local_list = cc->write_thread_list;
+ local_list.next->prev = &local_list;
+ local_list.prev->next = &local_list;
+ INIT_LIST_HEAD(&cc->write_thread_list);
+
+ spin_unlock_irq(&cc->write_thread_wait.lock);
+
+ blk_start_plug(&plug);
+ do {
+ struct dm_crypt_io *io = container_of(local_list.next,
+ struct dm_crypt_io, list);
+ list_del(&io->list);
+ kcryptd_io_write(io);
+ } while (!list_empty(&local_list));
+ blk_finish_plug(&plug);
+ }
+ return 0;
+}
+
static void kcryptd_crypt_write_io_submit(struct dm_crypt_io *io)
{
struct crypt_config *cc = io->cc;
+ unsigned long flags;

- INIT_WORK(&io->work, kcryptd_io_write);
- queue_work(cc->io_queue, &io->work);
+ 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);
+ spin_unlock_irqrestore(&cc->write_thread_wait.lock, flags);
}

static void kcryptd_crypt_write_convert(struct dm_crypt_io *io)
@@ -1299,6 +1360,9 @@ static void crypt_dtr(struct dm_target *ti)
kfree(cc->crypt_threads);
}

+ if (cc->write_thread)
+ kthread_stop(cc->write_thread);
+
if (cc->io_queue)
destroy_workqueue(cc->io_queue);

@@ -1669,6 +1733,18 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
}
}

+ init_waitqueue_head(&cc->write_thread_wait);
+ INIT_LIST_HEAD(&cc->write_thread_list);
+
+ cc->write_thread = kthread_create(dmcrypt_write, cc, "dmcrypt_write");
+ if (IS_ERR(cc->write_thread)) {
+ ret = PTR_ERR(cc->write_thread);
+ cc->write_thread = NULL;
+ ti->error = "Couldn't spawn write thread";
+ goto bad;
+ }
+ wake_up_process(cc->write_thread);
+
ti->num_flush_requests = 1;
ti->discard_zeroes_data_unsupported = true;

--
1.7.10.4

--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel
 

Thread Tools




All times are GMT. The time now is 05:11 PM.

VBulletin, Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Relevant URLs by vBSEO ©2007, Crawlability, Inc.
Copyright 2007 - 2008, www.linux-archive.org