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Remove an avoidable 3ms delay on some dm-raid1 and kcopyd I/O.
It is specified that any submitted bio without BIO_RW_SYNC flag may plug the
queue (i.e. block the requests from being dispatched to the physical device).
The queue is unplugged when the caller calls blk_unplug() function. Usually, the
sequence is that someone calls submit_bh to submit IO on a buffer. The IO plugs
the queue and waits (to be possibly joined with other adjacent bios). Then, when
the caller calls wait_on_buffer(), it unplugs the queue and submits the IOs to
the disk.
This was happenning:
When doing O_SYNC writes, function fsync_buffers_list() submits a list of
bios to dm_raid1, the bios are added to dm_raid1 write queue and kmirrord is
woken up.
fsync_buffers_list() calls wait_on_buffer(). That unplugs the queue, but
there are no bios on the device queue as they are still in the dm_raid1 queue.
wait_on_buffer() starts waiting until the IO is finished.
kmirrord is scheduled, kmirrord takes bios and submits them to the devices.
The submitted bio plugs the harddisk queue but there is no one to unplug it.
(The process that called wait_on_buffer() is already sleeping.)
So there is a 3ms timeout, after which the queues on the harddisks are
unplugged and requests are processed.
This 3ms timeout meant that in certain workloads (e.g. O_SYNC, 8kb writes),
dm-raid1 is 10 times slower than md raid1.
Every time we submit something asynchronously via dm_io, we must unplug the
queue actually to send the request to the device.
This patch adds an unplug call to kmirrord - while processing requests, it keeps
the queue plugged (so that adjacent bios can be merged); when it finishes
processing all the bios, it unplugs the queue to submit the bios.
It also fixes kcopyd which has the same potential problem. All kcopyd requests
are submitted with BIO_RW_SYNC.
Signed-off-by: Mikulas Patocka <[email protected]>
Signed-off-by: Alasdair G Kergon <[email protected]>
Acked-by: Jens Axboe <[email protected]>
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Publish the dm-io, dm-log and dm-kcopyd headers in include/linux.
Signed-off-by: Alasdair G Kergon <[email protected]>
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Clean up the dm-io interface to prepare for publishing it in include/linux.
Signed-off-by: Heinz Mauelshagen <[email protected]>
Signed-off-by: Alasdair G Kergon <[email protected]>
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Rename 'error' to 'error_bits' for clarity.
Signed-off-by: Alasdair G Kergon <[email protected]>
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write_err is an unsigned long used with set_bit() so should not be passed
around as unsigned int.
http://bugzilla.kernel.org/show_bug.cgi?id=10271
Signed-off-by: Alasdair G Kergon <[email protected]>
Cc: Heiko Carstens <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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As bi_end_io is only called once when the reqeust is complete,
the 'size' argument is now redundant. Remove it.
Now there is no need for bio_endio to subtract the size completed
from bi_size. So don't do that either.
While we are at it, change bi_end_io to return void.
Signed-off-by: Neil Brown <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
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bio_alloc_bioset() will return NULL if 'num_vecs' is too large.
Use bio_get_nr_vecs() to get estimation of maximum number.
Cc: [email protected]
Signed-off-by: "Jun'ichi Nomura" <[email protected]>
Signed-off-by: Alasdair G Kergon <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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Remove old dm-io interface.
Signed-off-by: Milan Broz <[email protected]>
Signed-off-by: Alasdair G Kergon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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Add a new API to dm-io.c that uses a private mempool and bio_set for each
client.
The new functions to use are dm_io_client_create(), dm_io_client_destroy(),
dm_io_client_resize() and dm_io().
Signed-off-by: Heinz Mauelshagen <[email protected]>
Signed-off-by: Alasdair G Kergon <[email protected]>
Cc: Milan Broz <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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Introduce struct dm_io_client to prepare for per-client mempools and bio_sets.
Temporary functions bios() and io_pool() choose between the per-client
structures and the global ones so the old and new interfaces can co-exist.
Make error_bits optional.
Signed-off-by: Heinz Mauelshagen <[email protected]>
Signed-off-by: Alasdair G Kergon <[email protected]>
Cc: Milan Broz <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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Delay decrementing the 'struct io' reference count until after the bio has
been freed so that a bio destructor function may reference it. Required by a
later patch.
Signed-off-by: Heinz Mauelshagen <[email protected]>
Signed-off-by: Alasdair G Kergon <[email protected]>
Cc: Milan Broz <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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Currently we scale the mempool sizes depending on memory installed
in the machine, except for the bio pool itself which sits at a fixed
256 entry pre-allocation.
There's really no point in "optimizing" this OOM path, we just need
enough preallocated to make progress. A single unit is enough, lets
scale it down to 2 just to be on the safe side.
This patch saves ~150kb of pinned kernel memory on a 32-bit box.
Signed-off-by: Jens Axboe <[email protected]>
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The existing code allocates an extra slot in bi_io_vec[] and uses it to store
the region number.
This patch hides the extra slot from bio_add_page() so the region number can't
get overwritten.
Also remove a hard-coded SECTOR_SHIFT and fix a typo in a comment.
Signed-off-by: Heinz Mauelshagen <[email protected]>
Signed-off-by: Alasdair G Kergon <[email protected]>
Cc: Milan Broz <[email protected]>
Cc: [email protected]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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This patch changes several mempool users, all of which are basically just
wrappers around kmalloc(), to use the common mempool_kmalloc/kfree, rather
than their own wrapper function, removing a bunch of duplicated code.
Signed-off-by: Matthew Dobson <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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- added typedef unsigned int __nocast gfp_t;
- replaced __nocast uses for gfp flags with gfp_t - it gives exactly
the same warnings as far as sparse is concerned, doesn't change
generated code (from gcc point of view we replaced unsigned int with
typedef) and documents what's going on far better.
Signed-off-by: Al Viro <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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Jens:
->bi_set is totally unnecessary bloat of struct bio. Just define a proper
destructor for the bio and it already knows what bio_set it belongs too.
Peter:
Fixed the bugs.
Signed-off-by: Jens Axboe <[email protected]>
Signed-off-by: Peter Osterlund <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
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