> On 5/24/2021 1:10 PM, Bart Van Assche wrote: > > On 5/24/21 1:36 AM, Can Guo wrote: > >> Current UFS IRQ handler is completely wrapped by host lock, and because > >> ufshcd_send_command() is also protected by host lock, when IRQ handler > >> fires, not only the CPU running the IRQ handler cannot send new > requests, > >> the rest CPUs can neither. Move the host lock wrapping the IRQ handler > into > >> specific branches, i.e., ufshcd_uic_cmd_compl(), ufshcd_check_errors(), > >> ufshcd_tmc_handler() and ufshcd_transfer_req_compl(). Meanwhile, to > further > >> reduce occpuation of host lock in ufshcd_transfer_req_compl(), host lock > is > >> no longer required to call __ufshcd_transfer_req_compl(). As per test, the > >> optimization can bring considerable gain to random read/write > performance. > > > > > An additional question is whether it is necessary for v3.0 UFS devices > > to serialize the submission path against the completion path? Multiple > > high-performance SCSI LLDs support hardware with separate submission > and > > completion queues and hence do not need any serialization between the > > submission and the completion path. I'm asking this because it is likely > > that sooner or later multiqueue support will be added in the UFS > > specification. Benefiting from multiqueue support will require to rework > > locking in the UFS driver anyway. > > > Hi Bart, > No it's not necessary to serialize both the paths. I think this series > attempts to remove this serialization to a certain degree, which is > what's giving the performance improvement. > > Even if multiqueue support would be available in the future, I think > this change is apt now for the current available specification. I agree - this looks like the harbinger of a major change, And going further with respect of hw queues, will need the spec support - e.g. doorbell per lane, etc. Thanks, Avri > > Thanks, > > > > Bart. > > > > > Thanks, > -asd > > -- > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora > Forum, > Linux Foundation Collaborative Project
