Hi Martin,
Can you review this patch and pull it into scsi since Nicholas has
been out for awhile?
I have tested this patch and really like the performance enhancements
as a result of it.
Thanks,
Bryant
On 4/19/18 1:29 PM, Andrei Vagin wrote:
> Hello Nicholas,
>
> What do you think about this patch?
>
> Thanks,
> Andrei
>
> On Wed, Mar 21, 2018 at 11:55:02PM -0700, Andrei Vagin wrote:
>> There are two advantages:
>> * Direct I/O allows to avoid the write-back cache, so it reduces
>> affects to other processes in the system.
>> * Async I/O allows to handle a few commands concurrently.
>>
>> DIO + AIO shows a better perfomance for random write operations:
>>
>> Mode: O_DSYNC Async: 1
>> $ ./fio --bs=4K --direct=1 --rw=randwrite --ioengine=libaio --iodepth=64 --name=/dev/sda --runtime=20 --numjobs=2
>> WRITE: bw=45.9MiB/s (48.1MB/s), 21.9MiB/s-23.0MiB/s (22.0MB/s-25.2MB/s), io=919MiB (963MB), run=20002-20020msec
>>
>> Mode: O_DSYNC Async: 0
>> $ ./fio --bs=4K --direct=1 --rw=randwrite --ioengine=libaio --iodepth=64 --name=/dev/sdb --runtime=20 --numjobs=2
>> WRITE: bw=1607KiB/s (1645kB/s), 802KiB/s-805KiB/s (821kB/s-824kB/s), io=31.8MiB (33.4MB), run=20280-20295msec
>>
>> Known issue:
>>
>> DIF (PI) emulation doesn't work when a target uses async I/O, because
>> DIF metadata is saved in a separate file, and it is another non-trivial
>> task how to synchronize writing in two files, so that a following read
>> operation always returns a consisten metadata for a specified block.
>>
>> v2: fix comments from Christoph Hellwig
>>
>> Cc: "Nicholas A. Bellinger" <nab@xxxxxxxxxxxxxxx>
>> Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
>> Cc: Bryant G. Ly <bryantly@xxxxxxxxxxxxxxxxxx>
>> Tested-by: Bryant G. Ly <bryantly@xxxxxxxxxxxxxxxxxx>
>> Signed-off-by: Andrei Vagin <avagin@xxxxxxxxxx>
>> ---
>> drivers/target/target_core_file.c | 137 ++++++++++++++++++++++++++++++++++----
>> drivers/target/target_core_file.h | 1 +
>> 2 files changed, 124 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c
>> index 9b2c0c773022..16751ae55d7b 100644
>> --- a/drivers/target/target_core_file.c
>> +++ b/drivers/target/target_core_file.c
>> @@ -250,6 +250,84 @@ static void fd_destroy_device(struct se_device *dev)
>> }
>> }
>>
>> +struct target_core_file_cmd {
>> + unsigned long len;
>> + struct se_cmd *cmd;
>> + struct kiocb iocb;
>> +};
>> +
>> +static void cmd_rw_aio_complete(struct kiocb *iocb, long ret, long ret2)
>> +{
>> + struct target_core_file_cmd *cmd;
>> +
>> + cmd = container_of(iocb, struct target_core_file_cmd, iocb);
>> +
>> + if (ret != cmd->len)
>> + target_complete_cmd(cmd->cmd, SAM_STAT_CHECK_CONDITION);
>> + else
>> + target_complete_cmd(cmd->cmd, SAM_STAT_GOOD);
>> +
>> + kfree(cmd);
>> +}
>> +
>> +static sense_reason_t
>> +fd_execute_rw_aio(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
>> + enum dma_data_direction data_direction)
>> +{
>> + int is_write = !(data_direction == DMA_FROM_DEVICE);
>> + struct se_device *dev = cmd->se_dev;
>> + struct fd_dev *fd_dev = FD_DEV(dev);
>> + struct file *file = fd_dev->fd_file;
>> + struct target_core_file_cmd *aio_cmd;
>> + struct iov_iter iter = {};
>> + struct scatterlist *sg;
>> + struct bio_vec *bvec;
>> + ssize_t len = 0;
>> + int ret = 0, i;
>> +
>> + aio_cmd = kmalloc(sizeof(struct target_core_file_cmd), GFP_KERNEL);
>> + if (!aio_cmd)
>> + return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
>> +
>> + bvec = kcalloc(sgl_nents, sizeof(struct bio_vec), GFP_KERNEL);
>> + if (!bvec) {
>> + kfree(aio_cmd);
>> + return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
>> + }
>> +
>> + for_each_sg(sgl, sg, sgl_nents, i) {
>> + bvec[i].bv_page = sg_page(sg);
>> + bvec[i].bv_len = sg->length;
>> + bvec[i].bv_offset = sg->offset;
>> +
>> + len += sg->length;
>> + }
>> +
>> + iov_iter_bvec(&iter, ITER_BVEC | is_write, bvec, sgl_nents, len);
>> +
>> + aio_cmd->cmd = cmd;
>> + aio_cmd->len = len;
>> + aio_cmd->iocb.ki_pos = cmd->t_task_lba * dev->dev_attrib.block_size;
>> + aio_cmd->iocb.ki_filp = file;
>> + aio_cmd->iocb.ki_complete = cmd_rw_aio_complete;
>> + aio_cmd->iocb.ki_flags = IOCB_DIRECT;
>> +
>> + if (is_write && (cmd->se_cmd_flags & SCF_FUA))
>> + aio_cmd->iocb.ki_flags |= IOCB_DSYNC;
>> +
>> + if (is_write)
>> + ret = call_write_iter(file, &aio_cmd->iocb, &iter);
>> + else
>> + ret = call_read_iter(file, &aio_cmd->iocb, &iter);
>> +
>> + kfree(bvec);
>> +
>> + if (ret != -EIOCBQUEUED)
>> + cmd_rw_aio_complete(&aio_cmd->iocb, ret, 0);
>> +
>> + return 0;
>> +}
>> +
>> static int fd_do_rw(struct se_cmd *cmd, struct file *fd,
>> u32 block_size, struct scatterlist *sgl,
>> u32 sgl_nents, u32 data_length, int is_write)
>> @@ -527,7 +605,7 @@ fd_execute_unmap(struct se_cmd *cmd, sector_t lba, sector_t nolb)
>> }
>>
>> static sense_reason_t
>> -fd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
>> +fd_execute_rw_buffered(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
>> enum dma_data_direction data_direction)
>> {
>> struct se_device *dev = cmd->se_dev;
>> @@ -537,16 +615,6 @@ fd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
>> sense_reason_t rc;
>> int ret = 0;
>> /*
>> - * We are currently limited by the number of iovecs (2048) per
>> - * single vfs_[writev,readv] call.
>> - */
>> - if (cmd->data_length > FD_MAX_BYTES) {
>> - pr_err("FILEIO: Not able to process I/O of %u bytes due to"
>> - "FD_MAX_BYTES: %u iovec count limitation\n",
>> - cmd->data_length, FD_MAX_BYTES);
>> - return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
>> - }
>> - /*
>> * Call vectorized fileio functions to map struct scatterlist
>> * physical memory addresses to struct iovec virtual memory.
>> */
>> @@ -620,14 +688,39 @@ fd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
>> return 0;
>> }
>>
>> +static sense_reason_t
>> +fd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
>> + enum dma_data_direction data_direction)
>> +{
>> + struct se_device *dev = cmd->se_dev;
>> + struct fd_dev *fd_dev = FD_DEV(dev);
>> +
>> + /*
>> + * We are currently limited by the number of iovecs (2048) per
>> + * single vfs_[writev,readv] call.
>> + */
>> + if (cmd->data_length > FD_MAX_BYTES) {
>> + pr_err("FILEIO: Not able to process I/O of %u bytes due to"
>> + "FD_MAX_BYTES: %u iovec count limitation\n",
>> + cmd->data_length, FD_MAX_BYTES);
>> + return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
>> + }
>> +
>> + if (fd_dev->fbd_flags & FDBD_HAS_ASYNC_IO)
>> + return fd_execute_rw_aio(cmd, sgl, sgl_nents, data_direction);
>> + return fd_execute_rw_buffered(cmd, sgl, sgl_nents, data_direction);
>> +}
>> +
>> enum {
>> - Opt_fd_dev_name, Opt_fd_dev_size, Opt_fd_buffered_io, Opt_err
>> + Opt_fd_dev_name, Opt_fd_dev_size, Opt_fd_buffered_io,
>> + Opt_fd_async_io, Opt_err
>> };
>>
>> static match_table_t tokens = {
>> {Opt_fd_dev_name, "fd_dev_name=%s"},
>> {Opt_fd_dev_size, "fd_dev_size=%s"},
>> {Opt_fd_buffered_io, "fd_buffered_io=%d"},
>> + {Opt_fd_async_io, "fd_async_io=%d"},
>> {Opt_err, NULL}
>> };
>>
>> @@ -693,6 +786,21 @@ static ssize_t fd_set_configfs_dev_params(struct se_device *dev,
>>
>> fd_dev->fbd_flags |= FDBD_HAS_BUFFERED_IO_WCE;
>> break;
>> + case Opt_fd_async_io:
>> + ret = match_int(args, &arg);
>> + if (ret)
>> + goto out;
>> + if (arg != 1) {
>> + pr_err("bogus fd_async_io=%d value\n", arg);
>> + ret = -EINVAL;
>> + goto out;
>> + }
>> +
>> + pr_debug("FILEIO: Using async I/O"
>> + " operations for struct fd_dev\n");
>> +
>> + fd_dev->fbd_flags |= FDBD_HAS_ASYNC_IO;
>> + break;
>> default:
>> break;
>> }
>> @@ -709,10 +817,11 @@ static ssize_t fd_show_configfs_dev_params(struct se_device *dev, char *b)
>> ssize_t bl = 0;
>>
>> bl = sprintf(b + bl, "TCM FILEIO ID: %u", fd_dev->fd_dev_id);
>> - bl += sprintf(b + bl, " File: %s Size: %llu Mode: %s\n",
>> + bl += sprintf(b + bl, " File: %s Size: %llu Mode: %s Async: %d\n",
>> fd_dev->fd_dev_name, fd_dev->fd_dev_size,
>> (fd_dev->fbd_flags & FDBD_HAS_BUFFERED_IO_WCE) ?
>> - "Buffered-WCE" : "O_DSYNC");
>> + "Buffered-WCE" : "O_DSYNC",
>> + !!(fd_dev->fbd_flags & FDBD_HAS_ASYNC_IO));
>> return bl;
>> }
>>
>> diff --git a/drivers/target/target_core_file.h b/drivers/target/target_core_file.h
>> index 53be5ffd3261..929b1ecd544e 100644
>> --- a/drivers/target/target_core_file.h
>> +++ b/drivers/target/target_core_file.h
>> @@ -22,6 +22,7 @@
>> #define FBDF_HAS_PATH 0x01
>> #define FBDF_HAS_SIZE 0x02
>> #define FDBD_HAS_BUFFERED_IO_WCE 0x04
>> +#define FDBD_HAS_ASYNC_IO 0x08
>> #define FDBD_FORMAT_UNIT_SIZE 2048
>>
>> struct fd_dev {
>> --
>> 2.13.6
>>
