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Petersen" , Mike Christie , linux-scsi@vger.kernel.org, target-devel@vger.kernel.org Cc: Bodo Stroesser Subject: [PATCH 3/3] scsi: target: tcmu: optimize scatter_data_area Date: Thu, 10 Sep 2020 17:50:41 +0200 Message-Id: <20200910155041.17654-4-bstroesser@ts.fujitsu.com> X-Mailer: git-send-email 2.12.3 In-Reply-To: <20200910155041.17654-1-bstroesser@ts.fujitsu.com> References: <20200910155041.17654-1-bstroesser@ts.fujitsu.com> Sender: target-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: target-devel@vger.kernel.org scatter_data_area has two purposes: 1) create the iovs for data area buffer of a SCSI cmd 2) If there is data in DMA_TO_DEVICE direction, it copies the data from sg_list to data area buffer. Both is done in a common loop. In case of DMA_FROM_DEVICE data transfer, scatter_data_area is called with parameter copy_data = false. But this flag is used just to skip memcpy() for data, while radix_tree_lookup still is called for every dbi of the area area buffer, and kmap and kunmap are called for every page from sg_list and data_area as well as flush_dcache_page() for the data area pages. Since the only thing to do with copy_data = false would be to set up the iovs, this is a noticeable overhead. Therefore I reworked the iov creation in the main loop of scatter_data_area providing the new function new_block_to_iov. Based on this I created the short new function tcmu_setup_iovs that only writes the iovs with no overhead. This new function is now called instead of scatter_data_area for bidi buffers and for data buffers in those cases, where memcpy would have been skipped. Signed-off-by: Bodo Stroesser --- drivers/target/target_core_user.c | 139 +++++++++++++++++--------------------- 1 file changed, 63 insertions(+), 76 deletions(-) diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c index 5587bd4d1060..18798c5422c7 100644 --- a/drivers/target/target_core_user.c +++ b/drivers/target/target_core_user.c @@ -181,6 +181,8 @@ struct tcmu_cmd { uint32_t dbi_cur; uint32_t *dbi; + uint32_t data_len_bidi; + unsigned long deadline; #define TCMU_CMD_BIT_EXPIRED 0 @@ -579,9 +581,47 @@ static inline void tcmu_cmd_set_block_cnts(struct tcmu_cmd *cmd) len += se_cmd->t_bidi_data_sg[i].length; cmd->dbi_bidi_cnt = DIV_ROUND_UP(len, DATA_BLOCK_SIZE); cmd->dbi_cnt += cmd->dbi_bidi_cnt; + cmd->data_len_bidi = len; } } +static int new_block_to_iov(struct tcmu_dev *udev, struct tcmu_cmd *cmd, + struct iovec **iov, int prev_dbi, int *remain) +{ + /* Get the next dbi */ + int dbi = tcmu_cmd_get_dbi(cmd); + /* Do not add more than DATA_BLOCK_SIZE to iov */ + int len = min_t(int, DATA_BLOCK_SIZE, *remain); + + *remain -= len; + /* + * The following code will gather and map the blocks to the same iovec + * when the blocks are all next to each other. + */ + if (dbi != prev_dbi + 1) { + /* dbi is not next to previous dbi, so start new iov */ + if (prev_dbi >= 0) + (*iov)++; + /* write offset relative to mb_addr */ + (*iov)->iov_base = (void __user *) + (udev->data_off + dbi * DATA_BLOCK_SIZE); + } + (*iov)->iov_len += len; + + return dbi; +} + +static void tcmu_setup_iovs(struct tcmu_dev *udev, struct tcmu_cmd *cmd, + struct iovec **iov, int data_length) +{ + /* start value of dbi + 1 must not be a valid dbi */ + int dbi = -2; + + /* We prepare the IOVs for DMA_FROM_DEVICE transfer direction */ + while (data_length > 0) + dbi = new_block_to_iov(udev, cmd, iov, dbi, &data_length); +} + static struct tcmu_cmd *tcmu_alloc_cmd(struct se_cmd *se_cmd) { struct se_device *se_dev = se_cmd->se_dev; @@ -646,45 +686,22 @@ static inline size_t head_to_end(size_t head, size_t size) return size - head; } -static inline void new_iov(struct iovec **iov, bool first) -{ - struct iovec *iovec; - - if (!first) - (*iov)++; - - iovec = *iov; - memset(iovec, 0, sizeof(struct iovec)); -} - #define UPDATE_HEAD(head, used, size) smp_store_release(&head, ((head % size) + used) % size) -/* offset is relative to mb_addr */ -static inline size_t get_block_offset_user(struct tcmu_dev *dev, - int dbi, int remaining) -{ - return dev->data_off + dbi * DATA_BLOCK_SIZE + - DATA_BLOCK_SIZE - remaining; -} - -static inline size_t iov_tail(struct iovec *iov) -{ - return (size_t)iov->iov_base + iov->iov_len; -} - -static void scatter_data_area(struct tcmu_dev *udev, - struct tcmu_cmd *tcmu_cmd, struct scatterlist *data_sg, - unsigned int data_nents, struct iovec **iov, bool copy_data) +static void scatter_data_area(struct tcmu_dev *udev, struct tcmu_cmd *tcmu_cmd, + struct iovec **iov) { - int i, dbi; + struct se_cmd *se_cmd = tcmu_cmd->se_cmd; + /* start value of dbi + 1 must not be a valid dbi */ + int i, dbi = -2; int block_remaining = 0; + int data_len = se_cmd->data_length; void *from, *to = NULL; - size_t copy_bytes, to_offset, offset; + size_t copy_bytes, offset; struct scatterlist *sg; struct page *page; - bool first = true; - for_each_sg(data_sg, sg, data_nents, i) { + for_each_sg(se_cmd->t_data_sg, sg, se_cmd->t_data_nents, i) { int sg_remaining = sg->length; from = kmap_atomic(sg_page(sg)) + sg->offset; while (sg_remaining > 0) { @@ -694,50 +711,19 @@ static void scatter_data_area(struct tcmu_dev *udev, kunmap_atomic(to); } - block_remaining = DATA_BLOCK_SIZE; - dbi = tcmu_cmd_get_dbi(tcmu_cmd); + /* get next dbi and add to IOVs */ + dbi = new_block_to_iov(udev, tcmu_cmd, iov, dbi, + &data_len); page = tcmu_get_block_page(udev, dbi); to = kmap_atomic(page); + block_remaining = DATA_BLOCK_SIZE; } - /* - * Covert to virtual offset of the ring data area. - */ - to_offset = get_block_offset_user(udev, dbi, - block_remaining); - - /* - * The following code will gather and map the blocks - * to the same iovec when the blocks are all next to - * each other. - */ copy_bytes = min_t(size_t, sg_remaining, block_remaining); - if (!first && to_offset == iov_tail(*iov)) { - /* - * Will append to the current iovec, because - * the current block page is next to the - * previous one. - */ - (*iov)->iov_len += copy_bytes; - } else { - /* - * Will allocate a new iovec because we are - * first time here or the current block page - * is not next to the previous one. - */ - new_iov(iov, first); - (*iov)->iov_base = (void __user *)to_offset; - (*iov)->iov_len = copy_bytes; - first = false; - } - - if (copy_data) { - offset = DATA_BLOCK_SIZE - block_remaining; - memcpy(to + offset, - from + sg->length - sg_remaining, - copy_bytes); - } + offset = DATA_BLOCK_SIZE - block_remaining; + memcpy(to + offset, from + sg->length - sg_remaining, + copy_bytes); sg_remaining -= copy_bytes; block_remaining -= copy_bytes; @@ -1010,7 +996,6 @@ static int queue_cmd_ring(struct tcmu_cmd *tcmu_cmd, sense_reason_t *scsi_err) int iov_cnt, iov_bidi_cnt, cmd_id; uint32_t cmd_head; uint64_t cdb_off; - bool copy_to_data_area; /* size of data buffer needed */ size_t data_length = (size_t)tcmu_cmd->dbi_cnt * DATA_BLOCK_SIZE; @@ -1084,17 +1069,19 @@ static int queue_cmd_ring(struct tcmu_cmd *tcmu_cmd, sense_reason_t *scsi_err) /* prepare iov list and copy data to data area if necessary */ tcmu_cmd_reset_dbi_cur(tcmu_cmd); iov = &entry->req.iov[0]; - copy_to_data_area = (se_cmd->data_direction == DMA_TO_DEVICE - || se_cmd->se_cmd_flags & SCF_BIDI); - scatter_data_area(udev, tcmu_cmd, se_cmd->t_data_sg, - se_cmd->t_data_nents, &iov, copy_to_data_area); + + if (se_cmd->data_direction == DMA_TO_DEVICE || + se_cmd->se_cmd_flags & SCF_BIDI) + scatter_data_area(udev, tcmu_cmd, &iov); + else + tcmu_setup_iovs(udev, tcmu_cmd, &iov, se_cmd->data_length); + entry->req.iov_cnt = iov_cnt - iov_bidi_cnt; /* Handle BIDI commands */ if (se_cmd->se_cmd_flags & SCF_BIDI) { iov++; - scatter_data_area(udev, tcmu_cmd, se_cmd->t_bidi_data_sg, - se_cmd->t_bidi_data_nents, &iov, false); + tcmu_setup_iovs(udev, tcmu_cmd, &iov, tcmu_cmd->data_len_bidi); entry->req.iov_bidi_cnt = iov_bidi_cnt; }