On Fri, May 27, 2022 at 06:24:41AM -0600, Jens Axboe wrote:
> On 5/27/22 1:29 AM, Kanchan Joshi wrote:
> > On Thu, May 26, 2022 at 08:18:04PM +0530, Ankit Kumar wrote:
> >
> >> +void fio_nvme_uring_cmd_prep(struct nvme_uring_cmd *cmd, struct io_u *io_u,
> >> + struct iovec *iov)
> >> +{
> >> + struct nvme_data *data = FILE_ENG_DATA(io_u->file);
> >> + __u64 slba;
> >> + __u32 nlb;
> >> +
> >> + slba = io_u->offset / data->lba_size;
> >> + nlb = (io_u->xfer_buflen / data->lba_size) - 1;
> >> +
> >> + memset(cmd, 0, sizeof(struct nvme_uring_cmd));
> >
> > Is this better or setting remaining fields (which are not populated
> > down) to zero.
>
> Since lba_size is a power of 2, it would be a lot more efficient to take
> this division by non-constant out of the fast path and init a shift
> value:
>
> data->lba_shift = log2(data->lba_size);
>
> and change these to:
>
> slba = io_u->offset >> data->lba_shift;
>
> and ditto for nlb.
Thanks, will do this in v3
>
> >> + /* cdw10 and cdw11 represent starting lba */
> >> + cmd->cdw10 = slba & 0xffffffff;
> >> + cmd->cdw11 = slba >> 32;
> >> + /* cdw12 represent number of lba's for read/write */
> >> + cmd->cdw12 = nlb;
> >> + if (iov) {
> >> + iov->iov_base = io_u->xfer_buf;
> >> + iov->iov_len = io_u->xfer_buflen;
> >> + cmd->addr = (__u64)(uintptr_t)iov;
> >> + cmd->data_len = 1;
> >
> > Is this correct? Do we always get 1 vector to deal with.
>
> Yes
>
> --
> Jens Axboe
>
>
