Messages in this thread | | | Date | Fri, 25 Nov 2022 12:33:52 +0000 | Subject | Re: Why is MEGASAS_SAS_QD set to 256? | From | John Garry <> |
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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?
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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