Messages in this thread | | | Date | Wed, 16 Mar 2011 16:18:30 +0800 | Subject | Re: [PATCH 04/10] block: initial patch for on-stack per-task plugging | From | Shaohua Li <> |
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2011/1/22 Jens Axboe <jaxboe@fusionio.com>: > Signed-off-by: Jens Axboe <jaxboe@fusionio.com> > --- > block/blk-core.c | 357 ++++++++++++++++++++++++++++++++------------ > block/elevator.c | 6 +- > include/linux/blk_types.h | 2 + > include/linux/blkdev.h | 30 ++++ > include/linux/elevator.h | 1 + > include/linux/sched.h | 6 + > kernel/exit.c | 1 + > kernel/fork.c | 3 + > kernel/sched.c | 11 ++- > 9 files changed, 317 insertions(+), 100 deletions(-) > > diff --git a/block/blk-core.c b/block/blk-core.c > index 960f12c..42dbfcc 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -27,6 +27,7 @@ > #include <linux/writeback.h> > #include <linux/task_io_accounting_ops.h> > #include <linux/fault-inject.h> > +#include <linux/list_sort.h> > > #define CREATE_TRACE_POINTS > #include <trace/events/block.h> > @@ -213,7 +214,7 @@ static void blk_delay_work(struct work_struct *work) > > q = container_of(work, struct request_queue, delay_work.work); > spin_lock_irq(q->queue_lock); > - q->request_fn(q); > + __blk_run_queue(q); > spin_unlock_irq(q->queue_lock); > } Hi Jens, I have some questions about the per-task plugging. Since the request list is per-task, and each task delivers its requests at finish flush or schedule. But when one cpu delivers requests to global queue, other cpus don't know. This seems to have problem. For example: 1. get_request_wait() can only flush current task's request list, other cpus/tasks might still have a lot of requests, which aren't sent to request_queue. your ioc-rq-alloc branch is for this, right? Will it be pushed to 2.6.39 too? I'm wondering if we should limit per-task queue length. If there are enough requests there, we force a flush plug. 2. some APIs like blk_delay_work, which call __blk_run_queue() might not work. because other CPUs might not dispatch their requests to request queue. So __blk_run_queue will eventually find no requests, which might stall devices. Since one cpu doesn't know other cpus' request list, I'm wondering if there are other similar issues.
Thanks, Shaohua -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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