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linux-next/include
shaohua.li@intel.com 3ac0cc4508 block: hold queue if flush is running for non-queueable flush drive
In some drives, flush requests are non-queueable. When flush request is
running, normal read/write requests can't run. If block layer dispatches
such request, driver can't handle it and requeue it.  Tejun suggested we
can hold the queue when flush is running. This can avoid unnecessary
requeue.  Also this can improve performance. For example, we have
request flush1, write1, flush 2. flush1 is dispatched, then queue is
hold, write1 isn't inserted to queue. After flush1 is finished, flush2
will be dispatched. Since disk cache is already clean, flush2 will be
finished very soon, so looks like flush2 is folded to flush1.

In my test, the queue holding completely solves a regression introduced by
commit 53d63e6b0d:

    block: make the flush insertion use the tail of the dispatch list

    It's not a preempt type request, in fact we have to insert it
    behind requests that do specify INSERT_FRONT.

which causes about 20% regression running a sysbench fileio
workload.

Stable: 2.6.39 only

Cc: stable@kernel.org
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2011-05-06 11:36:25 -06:00
..
acpi Fix common misspellings 2011-03-31 11:26:23 -03:00
asm-generic Merge branch 'for-linus2' of git://git.profusion.mobi/users/lucas/linux-2.6 2011-04-07 11:14:49 -07:00
crypto
drm Merge branch 'for-linus2' of git://git.profusion.mobi/users/lucas/linux-2.6 2011-04-07 11:14:49 -07:00
keys libceph: Create a new key type "ceph". 2011-03-29 12:11:24 -07:00
linux block: hold queue if flush is running for non-queueable flush drive 2011-05-06 11:36:25 -06:00
math-emu
media Fix common misspellings 2011-03-31 11:26:23 -03:00
mtd
net net/9p: nwname should be an unsigned int 2011-04-15 15:26:15 -05:00
pcmcia pcmcia: re-enable Zoomed Video support 2011-02-20 12:47:34 +01:00
rdma
rxrpc Fix common misspellings 2011-03-31 11:26:23 -03:00
scsi Fix common misspellings 2011-03-31 11:26:23 -03:00
sound Merge branch 'for-linus2' of git://git.profusion.mobi/users/lucas/linux-2.6 2011-04-07 11:14:49 -07:00
staging [media] Altera FPGA firmware download module 2011-03-21 20:32:16 -03:00
target Fix common misspellings 2011-03-31 11:26:23 -03:00
trace block: make unplug timer trace event correspond to the schedule() unplug 2011-04-16 13:51:05 +02:00
video Fix common misspellings 2011-03-31 11:26:23 -03:00
xen Fix common misspellings 2011-03-31 11:26:23 -03:00
Kbuild