Messages in this thread | | | Subject | Re: Why is MEGASAS_SAS_QD set to 256? | From | Yu Kuai <> | Date | Sat, 26 Nov 2022 09:15:53 +0800 |
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Hi,
在 2022/11/25 20:33, John Garry 写道: > On 24/11/2022 03:45, Yu Kuai wrote: >> Hi, >> >> While upgrading kernel from 4.19 to 5.10, I found that fio 1 thread 4k >> sequential io performance is dropped(160Mib -> 100 Mib), root cause is >> that queue_depth is changed from 64 to 256. >> >> commit 6e73550670ed1c07779706bb6cf61b99c871fc42 >> scsi: megaraid_sas: Update optimal queue depth for SAS and NVMe devices >> >> diff --git a/drivers/scsi/megaraid/megaraid_sas.h >> b/drivers/scsi/megaraid/megaraid_sas.h >> index bd8184072bed..ddfbe6f6667a 100644 >> --- a/drivers/scsi/megaraid/megaraid_sas.h >> +++ b/drivers/scsi/megaraid/megaraid_sas.h >> @@ -2233,9 +2233,9 @@ enum MR_PD_TYPE { >> >> /* JBOD Queue depth definitions */ >> #define MEGASAS_SATA_QD 32 >> -#define MEGASAS_SAS_QD 64 >> +#define MEGASAS_SAS_QD 256 >> #define MEGASAS_DEFAULT_PD_QD 64 >> -#define MEGASAS_NVME_QD 32 >> +#define MEGASAS_NVME_QD 64 >> >> >> And with the default nr_requests 256, 256 queue_depth will make the >> elevator has no effect, specifically io can't be merged in this test >> case. Hence it doesn't make sense to me to set default queue_depth to >> 256. >> >> Is there any reason why MEGASAS_SAS_QD is changed to 64? >> >> Thanks, >> Kuai >> > > Which type of drive do you use?
SAS SSDs
BTW, I also test with nvme as well, the default elevator is deadline and queue_depth seems too small, and performance is far from optimal.
Current default values don't seem good to me... 😒
Thanks, Kuai > > JFYI, in case missed, there was this discussion on SCSI queue depth a > while ago: > https://lore.kernel.org/linux-scsi/4b50f067-a368-2197-c331-a8c981f5cd02@huawei.com/ > > > Thanks, > John > > > . >
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