Vivek Goyal d9449ce35a Fix regression in direct writes performance due to WRITE_ODIRECT flag removal ... There seems to be a regression in direct write path due to following commit in for-2.6.33 branch of block tree. commit 1af60fbd75 Author: Jeff Moyer <jmoyer@redhat.com> Date: Fri Oct 2 18:56:53 2009 -0400 block: get rid of the WRITE_ODIRECT flag Marking direct writes as WRITE_SYNC_PLUG instead of WRITE_ODIRECT, sets the NOIDLE flag in bio and hence in request. This tells CFQ to not expect more request from the queue and not idle on it (despite the fact that queue's think time is less and it is not seeky). So direct writers lose big time when competing with sequential readers. Using fio, I have run one direct writer and two sequential readers and following are the results with 2.6.32-rc7 kernel and with for-2.6.33 branch. Test ==== 1 direct writer and 2 sequential reader running simultaneously. [global] directory=/mnt/sdc/fio/ runtime=10 [seqwrite] rw=write size=4G direct=1 [seqread] rw=read size=2G numjobs=2 2.6.32-rc7 ========== direct writes: aggrb=2,968KB/s readers : aggrb=101MB/s for-2.6.33 branch ================= direct write: aggrb=19KB/s readers aggrb=137MB/s This patch brings back the WRITE_ODIRECT flag, with the difference that we don't set the BIO_RW_UNPLUG flag so that device is not unplugged after submission of request and an explicit unplug from submitter is required. That way we fix the jeff's issue of not enough merging taking place in aio path as well as make sure direct writes get their fair share. After the fix ============= for-2.6.33 + fix ---------------- direct writes: aggrb=2,728KB/s reads: aggrb=103MB/s Thanks Vivek Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>		2009-11-26 09:46:46 +01:00
..
acpi	ACPI: remove acpi_device_uid() and related stuff	2009-09-25 15:09:49 -04:00
asm-generic	block: add helpers to run flush_dcache_page() against a bio and a request's pages	2009-11-26 09:16:19 +01:00
crypto	Merge git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6	2009-09-11 09:38:37 -07:00
drm	Merge branch 'drm-next' of ../drm-next into drm-linus	2009-10-08 14:03:05 +10:00
keys	RxRPC: Use uX/sX rather than uintX_t/intX_t types	2009-09-16 00:01:13 -07:00
linux	Fix regression in direct writes performance due to WRITE_ODIRECT flag removal	2009-11-26 09:46:46 +01:00
math-emu
media	V4L/DVB (13019): video: initial support for ADV7180	2009-09-19 00:53:39 -03:00
mtd
net	net: Fix struct inet_timewait_sock bitfield annotation	2009-10-20 01:13:26 -07:00
pcmcia	PM / PCMCIA: Drop second argument of pcmcia_socket_dev_suspend()	2009-09-29 00:10:41 +02:00
rdma	trivial: fix typo "to to" in multiple files	2009-09-21 15:14:55 +02:00
rxrpc
scsi	[SCSI] libiscsi: iscsi_session_setup to allow for private space	2009-10-02 14:01:39 -05:00
sound	Merge branch 'topic/ymfpci' into for-linus	2009-09-10 15:33:09 +02:00
trace	Merge branch 'for-linus' of git://git.kernel.dk/linux-2.6-block	2009-10-04 12:39:14 -07:00
video	davinci-fb-frame-buffer-driver-for-ti-da8xx-omap-l1xx-v4	2009-09-23 07:39:51 -07:00
xen
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