Jens Axboe <[email protected]> writes: >> Comments would be greatly appreciated. > > It's hard to argue with the increased merging for your case. The task > plugs did originally work like you changed them to, not flushing until > the outermost plug was flushed. Unfortunately I don't quite remember > why I changed them, will have to do a bit of digging to refresh my > memory.
Let me know what you dig up. > For cases where we don't do any merging (like nvme), we always want to > flush. Well almost, if we start do utilize the batched submission, > then the plug would still potentially help (just for other reasons > than merging). It's never straight-forward. :) > And agree with Ming, this can be cleaned up substantially. I'd also Let me know if you have any issues with the v2 posting. > like to see some test results from the other end of the spectrum. Your > posted cased is clearly based case (we missed tons of merging, now we > don't), I'd like to see a normal case and a worst case result as well > so we have an idea of what this would do to latencies. As for other benchmark numbers, this work was inspired by two reports of lower performance after converting virtio_blk to use blk-mq in RHEL. The workloads were both synthetic, though. I'd be happy to run a battery of tests on the patch set, but if there is anything specific you want to see (besides a workload that will have no merges), let me know. I guess I should also mention that another solution to the problem might be the mythical mq I/O scheduler. :) Cheers, Jeff -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
