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Shaohua Li 4b27e1bb44 cfq-iosched: limit coop preemption ... CFQ has an optimization for cooperated applications. if several io-context have close requests, they will get boost. But the optimization get abused. Considering thread a, b, which work on one file. a reads sectors s, s+2, s+4, ...; b reads sectors s+1, s+3, s +5, ... Both a and b are sequential read, so they can open idle window. a reads a sector s and goes to idle window and wakeup b. b reads sector s+1, since in current implementation, cfq_should_preempt() thinks a and b are cooperators, b will preempt a. b then reads sector s+1 and goes to idle window and wakeup a. for the same reason, a will preempt b and reads s+2. a and b will continue the circle. The circle will be very long, and a and b will occupy whole disk queue. Other applications will nearly have no chance to run. Fix this limiting coop preempt until a queue is scheduled normally again. Signed-off-by: Shaohua Li <shaohua.li@intel.com> Acked-by: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>		15 years ago
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Kconfig	Make SCSI SG v4 driver enabled by default and remove EXPERIMENTAL dependency, since udev depends on BSG	16 years ago
Kconfig.iosched	…
Makefile	block: add blk-iopoll, a NAPI like approach for block devices	16 years ago
as-iosched.c	percpu: clean up percpu variable definitions	16 years ago
blk-barrier.c	block: allow large discard requests	16 years ago
blk-core.c	block: silently error unsupported empty barriers too	15 years ago
blk-exec.c	…
blk-integrity.c	block: fix improper kobject release in blk_integrity_unregister	16 years ago
blk-ioc.c	block: prevent possible io_context->refcount overflow	16 years ago
blk-iopoll.c	block: use interrupts disabled version of raise_softirq_irqoff()	16 years ago
blk-map.c	block: Use accessor functions for queue limits	16 years ago
blk-merge.c	block: Seperate read and write statistics of in_flight requests v2	16 years ago
blk-settings.c	blk-settings: fix function parameter kernel-doc notation	16 years ago
blk-softirq.c	…
blk-sysfs.c	Add missing blk_trace_remove_sysfs to be in pair with blk_trace_init_sysfs	16 years ago
blk-tag.c	block: use proper BLK_RW_ASYNC in blk_queue_start_tag()	16 years ago
blk-timeout.c	…
blk.h	block: implement mixed merge of different failfast requests	16 years ago
bsg.c	Driver-Core: extend devnode callbacks to provide permissions	16 years ago
cfq-iosched.c	cfq-iosched: limit coop preemption	15 years ago
compat_ioctl.c	block: Topology ioctls	16 years ago
deadline-iosched.c	…
elevator.c	elv_iosched_store(): fix strstrip() misuse	16 years ago
genhd.c	block: Seperate read and write statistics of in_flight requests v2	16 years ago
ioctl.c	block: Topology ioctls	16 years ago
noop-iosched.c	…
scsi_ioctl.c	block: call blk_scsi_ioctl_init()	16 years ago