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9937a5e2f3
linux/include
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Jens Axboe 9937a5e2f3 scsi: remove performance regression due to async queue run 
Commit c21e6beb removed our queue request_fn re-enter
protection, and defaulted to always running the queues from
kblockd to be safe. This was a known potential slow down,
but should be safe.

Unfortunately this is causing big performance regressions for
some, so we need to improve this logic. Looking into the details
of the re-enter, the real issue is on requeue of requests.

Requeue of requests upon seeing a BUSY condition from the device
ends up re-running the queue, causing traces like this:

scsi_request_fn()
        scsi_dispatch_cmd()
                scsi_queue_insert()
                        __scsi_queue_insert()
                                scsi_run_queue()
					scsi_request_fn()
						...

potentially causing the issue we want to avoid. So special
case the requeue re-run of the queue, but improve it to offload
the entire run of local queue and starved queue from a single
workqueue callback. This is a lot better than potentially
kicking off a workqueue run for each device seen.

This also fixes the issue of the local device going into recursion,
since the above mentioned commit never moved that queue run out
of line.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2011-05-17 11:04:44 +02:00
..
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 Merge branch 'for-linus' of git://git.kernel.dk/linux-2.6-block 2011-04-20 09:48:52 -07:00
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
rdma
rxrpc Fix common misspellings 2011-03-31 11:26:23 -03:00
scsi scsi: remove performance regression due to async queue run 2011-05-17 11:04:44 +02:00
sound Merge branch 'for-linus2' of git://git.profusion.mobi/users/lucas/linux-2.6 2011-04-07 11:14:49 -07:00
staging
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