Jens Axboe <axboe@xxxxxx> writes: > On 03/22/2016 02:12 PM, Jeff Moyer wrote: >> Hi, Jens, >> >> Jens Axboe <axboe@xxxxxx> writes: >> >>> If the device has write back caching, 'wb_cache_delay' delays by >>> this amount of usecs when a write completes before allowing more. >> >> What's the reason behind that? > > For classic write back caching, the cache can absorb a bunch of writes > shortly, which means that the completion cost only shows a small part > of the overall cost. This means that if we just throttle on > completion, then when the device starts committing to media, then > we'll end up starving other IO anyway. This knob is a way to attempt > to tame that. Ah, makes perfect sense. Thanks! -Jeff -- 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
