On 01/13/2017 12:04 PM, Hannes Reinecke wrote: > On 01/13/2017 09:15 AM, Hannes Reinecke wrote: >> On 01/11/2017 10:39 PM, Jens Axboe wrote: >>> Another year, another posting of this patchset. The previous posting >>> was here: >>> >>> https://www.spinics.net/lists/kernel/msg2406106.html >>> >>> (yes, I've skipped v5, it was fixes on top of v4, not the rework). >>> >>> I've reworked bits of this to get rid of the shadow requests, thanks >>> to Bart for the inspiration. The missing piece, for me, was the fact >>> that we have the tags->rqs[] indirection array already. I've done this >>> somewhat differently, though, by having the internal scheduler tag >>> map be allocated/torn down when an IO scheduler is attached or >>> detached. This also means that when we run without a scheduler, we >>> don't have to do double tag allocations, it'll work like before. >>> >>> The patchset applies on top of 4.10-rc3, or can be pulled here: >>> >>> git://git.kernel.dk/linux-block blk-mq-sched.6 >>> >> Well ... something's wrong here on my machine: >> [ .. ] Turns out that selecting CONFIG_DEFAULT_MQ_DEADLINE is the culprit; switching to CONFIG_DEFAULT_MQ_NONE and selecting mq-deadline after booting manually makes the problem go away. So there is a race condition during device init and switching the I/O scheduler. But the results from using mq-deadline are promising; the performance drop I've seen on older hardware seems to be resolved: mq iosched: seq read : io=13383MB, bw=228349KB/s, iops=57087 rand read : io=12876MB, bw=219709KB/s, iops=54927 seq write: io=14532MB, bw=247987KB/s, iops=61996 rand write: io=13779MB, bw=235127KB/s, iops=58781 mq default: seq read : io=13056MB, bw=222588KB/s, iops=55647 rand read : io=12908MB, bw=220069KB/s, iops=55017 seq write: io=13986MB, bw=238444KB/s, iops=59611 rand write: io=13733MB, bw=234128KB/s, iops=58532 sq default: seq read : io=10240MB, bw=194787KB/s, iops=48696 rand read : io=10240MB, bw=191374KB/s, iops=47843 seq write: io=10240MB, bw=245333KB/s, iops=61333 rand write: io=10240MB, bw=228239KB/s, iops=57059 measured on mpt2sas with SSD devices. Cheers, Hannes -- Dr. Hannes Reinecke Teamlead Storage & Networking hare@xxxxxxx +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG Nürnberg) -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
