On Wed, Aug 08, 2007 at 02:17:09PM +0400, Evgeniy Polyakov (johnpol@xxxxxxxxxxx) wrote: > This throttling mechanism allows to limit maximum amount of queued bios > per physical device. By default it is turned off and old block layer > behaviour with unlimited number of bios is used. When turned on (queue > limit is set to something different than -1U via blk_set_queue_limit()), > generic_make_request() will sleep until there is room in the queue. > number of bios is increased in generic_make_request() and reduced either > in bio_endio(), when bio is completely processed (bi_size is zero), and > recharged from original queue when new device is assigned to bio via > blk_set_bdev(). All oerations are not atomic, since we do not care about > precise number of bios, but a fact, that we are close or close enough to > the limit. > > Tested on distributed storage device - with limit of 2 bios it works > slow :) As addon I can cook up a patch to configure this via sysfs if needed. Thoughts? -- Evgeniy Polyakov - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
