Commit 2916405a authored by Li Feng's avatar Li Feng Committed by Fam Zheng
Browse files

block/nvme: optimize the performance of nvme driver based on vfio-pci 



When the IO size is larger than 2 pages, we move the the pointer one by
one in the pagelist, this is inefficient.

This is a simple benchmark result:

Before:
$ qemu-io -c 'write 0 1G' nvme://0000:00:04.0/1

wrote 1073741824/1073741824 bytes at offset 0
1 GiB, 1 ops; 0:00:02.41 (424.504 MiB/sec and 0.4146 ops/sec)

 $ qemu-io -c 'read 0 1G' nvme://0000:00:04.0/1

read 1073741824/1073741824 bytes at offset 0
1 GiB, 1 ops; 0:00:02.03 (503.055 MiB/sec and 0.4913 ops/sec)

After:
$ qemu-io -c 'write 0 1G' nvme://0000:00:04.0/1

wrote 1073741824/1073741824 bytes at offset 0
1 GiB, 1 ops; 0:00:02.17 (471.517 MiB/sec and 0.4605 ops/sec)

 $ qemu-io -c 'read 0 1G' nvme://0000:00:04.0/1

read 1073741824/1073741824 bytes at offset 0
1 GiB, 1 ops; 0:00:01.94 (526.770 MiB/sec and 0.5144 ops/sec)

Signed-off-by: default avatarLi Feng <lifeng1519@gmail.com>
Message-Id: <20181101103807.25862-1-lifeng1519@gmail.com>
Signed-off-by: default avatarFam Zheng <famz@redhat.com>
parent 147923b1

block/nvme.c

+6 −10
Original line number Diff line number Diff line
@@ -837,7 +837,7 @@ try_map: 
        }



        for (j = 0; j < qiov->iov[i].iov_len / s->page_size; j++) {

            pagelist[entries++] = iova + j * s->page_size;

            pagelist[entries++] = cpu_to_le64(iova + j * s->page_size);

        }

        trace_nvme_cmd_map_qiov_iov(s, i, qiov->iov[i].iov_base,

                                    qiov->iov[i].iov_len / s->page_size);
@@ -850,20 +850,16 @@ try_map: 
    case 0:

        abort();

    case 1:

        cmd->prp1 = cpu_to_le64(pagelist[0]);

        cmd->prp1 = pagelist[0];

        cmd->prp2 = 0;

        break;

    case 2:

        cmd->prp1 = cpu_to_le64(pagelist[0]);

        cmd->prp2 = cpu_to_le64(pagelist[1]);;

        cmd->prp1 = pagelist[0];

        cmd->prp2 = pagelist[1];

        break;

    default:

        cmd->prp1 = cpu_to_le64(pagelist[0]);

        cmd->prp2 = cpu_to_le64(req->prp_list_iova);

        for (i = 0; i < entries - 1; ++i) {

            pagelist[i] = cpu_to_le64(pagelist[i + 1]);

        }

        pagelist[entries - 1] = 0;

        cmd->prp1 = pagelist[0];

        cmd->prp2 = cpu_to_le64(req->prp_list_iova + sizeof(uint64_t));

        break;

    }

    trace_nvme_cmd_map_qiov(s, cmd, req, qiov, entries);