On Mon, Nov 04, 2013 at 03:36:24PM -0800, Kent Overstreet wrote:
> We get a measurable performance increase by handling this in the driver when
> we're already looping over the biovec, instead of handling it separately in
> generic_make_request() (or bio_add_page() originally)
>
> Signed-off-by: Kent Overstreet <k...@daterainc.com>
> ---
> drivers/block/mtip32xx/mtip32xx.c | 46
> +++++++++++++--------------------------
> 1 file changed, 15 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/block/mtip32xx/mtip32xx.c
> b/drivers/block/mtip32xx/mtip32xx.c
> index d4c669b..c5a7a96 100644
> --- a/drivers/block/mtip32xx/mtip32xx.c
> +++ b/drivers/block/mtip32xx/mtip32xx.c
> @@ -2648,24 +2648,6 @@ static void mtip_hw_submit_io(struct driver_data *dd,
> sector_t sector,
> }
>
> /*
> - * Release a command slot.
> - *
> - * @dd Pointer to the driver data structure.
> - * @tag Slot tag
> - *
> - * return value
> - * None
> - */
> -static void mtip_hw_release_scatterlist(struct driver_data *dd, int tag,
> - int unaligned)
> -{
> - struct semaphore *sem = unaligned ? &dd->port->cmd_slot_unal :
> - &dd->port->cmd_slot;
> - release_slot(dd->port, tag);
> - up(sem);
> -}
> -
> -/*
> * Obtain a command slot and return its associated scatter list.
> *
> * @dd Pointer to the driver data structure.
> @@ -4016,21 +3998,22 @@ static void mtip_make_request(struct request_queue
> *queue, struct bio *bio)
>
> sg = mtip_hw_get_scatterlist(dd, &tag, unaligned);
> if (likely(sg != NULL)) {
> - if (unlikely((bio)->bi_vcnt > MTIP_MAX_SG)) {
> - dev_warn(&dd->pdev->dev,
> - "Maximum number of SGL entries exceeded\n");
> - bio_io_error(bio);
> - mtip_hw_release_scatterlist(dd, tag, unaligned);
> - return;
> - }
> -
> /* Create the scatter list for this bio. */
> bio_for_each_segment(bvec, bio, iter) {
> - sg_set_page(&sg[nents],
> - bvec.bv_page,
> - bvec.bv_len,
> - bvec.bv_offset);
> - nents++;
> + if (unlikely(nents == MTIP_MAX_SG)) {
> + struct bio *split = bio_clone(bio, GFP_NOIO);
> +
Need to check for memory allocation failure here. Thanks,
Josef
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