On 2020/11/18 16:07, Christoph Hellwig wrote:
> Adding Damien who wrote this code.
Nope. It wasn't me. I think it was Stephen Bates:
commit 720b8ccc4500 ("blk-mq: Add a polling specific stats function")
So +Stephen.
>
> On Wed, Nov 18, 2020 at 09:47:46AM +0900, Dongjoo Seo wrote:
>> Current sleep time for hybrid polling is half of mean time.
>> The 'half' sleep time is good for minimizing the cpu utilization.
>> But, the problem is that its cpu utilization is still high.
>> this patch can help to minimize the cpu utilization side.
>>
>> Below 1,2 is my test hardware sets.
>>
>> 1. Intel(R) Core(TM) i7-7700 CPU @ 3.60GHz + Samsung 970 pro 1Tb
>> 2. Intel(R) Core(TM) i7-5820K CPU @ 3.30GHz + INTEL SSDPED1D480GA 480G
>>
>> | Classic Polling | Hybrid Polling | this Patch
>> -----------------------------------------------------------------
>> cpu util | IOPS(k) | cpu util | IOPS | cpu util | IOPS |
>> -----------------------------------------------------------------
>> 1. 99.96 | 491 | 56.98 | 467 | 35.98 | 442 |
>> -----------------------------------------------------------------
>> 2. 99.94 | 582 | 56.3 | 582 | 35.28 | 582 |
>>
>> cpu util means that sum of sys and user util.
>>
>> I used 4k rand read for this test.
>> because that case is worst case of I/O performance side.
>> below one is my fio setup.
>>
>> name=pollTest
>> ioengine=pvsync2
>> hipri
>> direct=1
>> size=100%
>> randrepeat=0
>> time_based
>> ramp_time=0
>> norandommap
>> refill_buffers
>> log_avg_msec=1000
>> log_max_value=1
>> group_reporting
>> filename=/dev/nvme0n1
>> [rd_rnd_qd_1_4k_1w]
>> bs=4k
>> iodepth=32
>> numjobs=[num of cpus]
>> rw=randread
>> runtime=60
>> write_bw_log=bw_rd_rnd_qd_1_4k_1w
>> write_iops_log=iops_rd_rnd_qd_1_4k_1w
>> write_lat_log=lat_rd_rnd_qd_1_4k_1w
>>
>> Thanks
>>
>> Signed-off-by: Dongjoo Seo <commisori28@xxxxxxxxx>
>> ---
>> block/blk-mq.c | 3 +--
>> 1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>> index 1b25ec2fe9be..c3d578416899 100644
>> --- a/block/blk-mq.c
>> +++ b/block/blk-mq.c
>> @@ -3749,8 +3749,7 @@ static unsigned long blk_mq_poll_nsecs(struct request_queue *q,
>> return ret;
>>
>> if (q->poll_stat[bucket].nr_samples)
>> - ret = (q->poll_stat[bucket].mean + 1) / 2;
>> -
>> + ret = (q->poll_stat[bucket].mean + 1) * 3 / 4;
>> return ret;
>> }
>>
>> --
>> 2.17.1
>>
> ---end quoted text---
>
--
Damien Le Moal
Western Digital Research
