[Virtio-fs] [PATCH RFC] virtiofs: improve io bandwidth by replacing pwrite with pwritev
Dr. David Alan Gilbert
dgilbert at redhat.com
Tue Aug 6 16:09:03 UTC 2019
* piaojun (piaojun at huawei.com) wrote:
> >From my test, write bandwidth will be improved greatly by replacing
> pwrite with pwritev, and the test result as below:
>
> ---
> pwrite:
> # fio -direct=1 -time_based -iodepth=64 -rw=randwrite -ioengine=libaio -bs=1M -size=1G -numjob=16 -runtime=30 -group_reporting -name=file -filename=/mnt/virtiofs/file
> file: (g=0): rw=randwrite, bs=1M-1M/1M-1M/1M-1M, ioengine=libaio, iodepth=64
> ...
> fio-2.13
> Starting 16 processes
> Jobs: 16 (f=16): [w(16)] [100.0% done] [0KB/886.0MB/0KB /s] [0/886/0 iops] [eta 00m:00s]
> file: (groupid=0, jobs=16): err= 0: pid=5799: Tue Aug 6 18:48:26 2019
> write: io=26881MB, bw=916988KB/s, iops=895, runt= 30018msec
>
> pwritev:
> # fio -direct=1 -time_based -iodepth=64 -rw=randwrite -ioengine=libaio -bs=1M -size=1G -numjob=16 -runtime=30 -group_reporting -name=file -filename=/mnt/virtiofs/file
> file: (g=0): rw=randwrite, bs=1M-1M/1M-1M/1M-1M, ioengine=libaio, iodepth=64
> ...
> fio-2.13
> Starting 16 processes
> Jobs: 16 (f=16): [w(16)] [100.0% done] [0KB/1793MB/0KB /s] [0/1793/0 iops] [eta 00m:00s]
> file: (groupid=0, jobs=16): err= 0: pid=6328: Tue Aug 6 18:22:17 2019
> write: io=52775MB, bw=1758.7MB/s, iops=1758, runt= 30009msec
OK, nice improvements.
> ---
>
> This patch introduces writev and pwritev and clean up *fuse_buf_copy*
> and its related code. I wonder if I'd better split it into two patches
> or other modification. I'm very glad for your suggestions.
It does need splitting; but I think there are some problems; it seems to
ignore most of the flags; in particular FUSE_BUF_PHYS_ADDR - I added
that to handle cases where it was a write() call from one DAX mapped
file to another. I suspect some of the other flags are relevant as
well.
Dave
> Thanks,
> Jun
>
> Signed-off-by: Jun Piao <piaojun at huawei.com>
> ---
> contrib/virtiofsd/buffer.c | 310 ++++---------------------------------
> contrib/virtiofsd/fuse_common.h | 15 +-
> contrib/virtiofsd/passthrough_ll.c | 2 +-
> contrib/virtiofsd/seccomp.c | 2 +
> 4 files changed, 37 insertions(+), 292 deletions(-)
>
> diff --git a/contrib/virtiofsd/buffer.c b/contrib/virtiofsd/buffer.c
> index 655be137..78f8d3e 100644
> --- a/contrib/virtiofsd/buffer.c
> +++ b/contrib/virtiofsd/buffer.c
> @@ -15,6 +15,7 @@
> #include <unistd.h>
> #include <errno.h>
> #include <assert.h>
> +#include <stdlib.h>
>
> size_t fuse_buf_size(const struct fuse_bufvec *bufv)
> {
> @@ -31,299 +32,40 @@ size_t fuse_buf_size(const struct fuse_bufvec *bufv)
> return size;
> }
>
> -static size_t min_size(size_t s1, size_t s2)
> +ssize_t fuse_buf_writev(fuse_req_t req,
> + struct fuse_bufvec *out_buf,
> + struct fuse_bufvec *in_buf,
> + enum fuse_buf_copy_flags flags)
> {
> - return s1 < s2 ? s1 : s2;
> -}
> -
> -static ssize_t fuse_buf_write(const struct fuse_buf *dst, size_t dst_off,
> - const struct fuse_buf *src, size_t src_off,
> - size_t len)
> -{
> - ssize_t res = 0;
> - size_t copied = 0;
> -
> - assert(!(src->flags & FUSE_BUF_PHYS_ADDR));
> - while (len) {
> - if (dst->flags & FUSE_BUF_FD_SEEK) {
> - res = pwrite(dst->fd, src->mem + src_off, len,
> - dst->pos + dst_off);
> - } else {
> - res = write(dst->fd, src->mem + src_off, len);
> - }
> - if (res == -1) {
> - if (!copied)
> - return -errno;
> - break;
> - }
> - if (res == 0)
> - break;
> -
> - copied += res;
> - if (!(dst->flags & FUSE_BUF_FD_RETRY))
> - break;
> -
> - src_off += res;
> - dst_off += res;
> - len -= res;
> - }
> -
> - return copied;
> -}
> -
> -static ssize_t fuse_buf_read(const struct fuse_buf *dst, size_t dst_off,
> - const struct fuse_buf *src, size_t src_off,
> - size_t len)
> -{
> - ssize_t res = 0;
> - size_t copied = 0;
> -
> - while (len) {
> - if (src->flags & FUSE_BUF_FD_SEEK) {
> - res = pread(src->fd, dst->mem + dst_off, len,
> - src->pos + src_off);
> - } else {
> - res = read(src->fd, dst->mem + dst_off, len);
> - }
> - if (res == -1) {
> - if (!copied)
> - return -errno;
> - break;
> - }
> - if (res == 0)
> - break;
> -
> - copied += res;
> - if (!(src->flags & FUSE_BUF_FD_RETRY))
> - break;
> -
> - dst_off += res;
> - src_off += res;
> - len -= res;
> - }
> -
> - return copied;
> -}
> -
> -static ssize_t fuse_buf_fd_to_fd(const struct fuse_buf *dst, size_t dst_off,
> - const struct fuse_buf *src, size_t src_off,
> - size_t len)
> -{
> - char buf[4096];
> - struct fuse_buf tmp = {
> - .size = sizeof(buf),
> - .flags = 0,
> - };
> - ssize_t res;
> - size_t copied = 0;
> -
> - tmp.mem = buf;
> -
> - while (len) {
> - size_t this_len = min_size(tmp.size, len);
> - size_t read_len;
> -
> - res = fuse_buf_read(&tmp, 0, src, src_off, this_len);
> - if (res < 0) {
> - if (!copied)
> - return res;
> - break;
> - }
> - if (res == 0)
> - break;
> -
> - read_len = res;
> - res = fuse_buf_write(dst, dst_off, &tmp, 0, read_len);
> - if (res < 0) {
> - if (!copied)
> - return res;
> - break;
> - }
> - if (res == 0)
> - break;
> -
> - copied += res;
> -
> - if (res < this_len)
> - break;
> -
> - dst_off += res;
> - src_off += res;
> - len -= res;
> - }
> -
> - return copied;
> -}
> -
> -#ifdef HAVE_SPLICE
> -static ssize_t fuse_buf_splice(const struct fuse_buf *dst, size_t dst_off,
> - const struct fuse_buf *src, size_t src_off,
> - size_t len, enum fuse_buf_copy_flags flags)
> -{
> - int splice_flags = 0;
> - off_t *srcpos = NULL;
> - off_t *dstpos = NULL;
> - off_t srcpos_val;
> - off_t dstpos_val;
> - ssize_t res;
> - size_t copied = 0;
> -
> - if (flags & FUSE_BUF_SPLICE_MOVE)
> - splice_flags |= SPLICE_F_MOVE;
> - if (flags & FUSE_BUF_SPLICE_NONBLOCK)
> - splice_flags |= SPLICE_F_NONBLOCK;
> -
> - if (src->flags & FUSE_BUF_FD_SEEK) {
> - srcpos_val = src->pos + src_off;
> - srcpos = &srcpos_val;
> - }
> - if (dst->flags & FUSE_BUF_FD_SEEK) {
> - dstpos_val = dst->pos + dst_off;
> - dstpos = &dstpos_val;
> - }
> -
> - while (len) {
> - res = splice(src->fd, srcpos, dst->fd, dstpos, len,
> - splice_flags);
> - if (res == -1) {
> - if (copied)
> - break;
> -
> - if (errno != EINVAL || (flags & FUSE_BUF_FORCE_SPLICE))
> - return -errno;
> -
> - /* Maybe splice is not supported for this combination */
> - return fuse_buf_fd_to_fd(dst, dst_off, src, src_off,
> - len);
> - }
> - if (res == 0)
> - break;
> -
> - copied += res;
> - if (!(src->flags & FUSE_BUF_FD_RETRY) &&
> - !(dst->flags & FUSE_BUF_FD_RETRY)) {
> - break;
> - }
> -
> - len -= res;
> - }
> -
> - return copied;
> -}
> -#else
> -static ssize_t fuse_buf_splice(const struct fuse_buf *dst, size_t dst_off,
> - const struct fuse_buf *src, size_t src_off,
> - size_t len, enum fuse_buf_copy_flags flags)
> -{
> - (void) flags;
> -
> - return fuse_buf_fd_to_fd(dst, dst_off, src, src_off, len);
> -}
> -#endif
> -
> -
> -static ssize_t fuse_buf_copy_one(fuse_req_t req,
> - const struct fuse_buf *dst, size_t dst_off,
> - const struct fuse_buf *src, size_t src_off,
> - size_t len, enum fuse_buf_copy_flags flags)
> -{
> - int src_is_fd = src->flags & FUSE_BUF_IS_FD;
> - int dst_is_fd = dst->flags & FUSE_BUF_IS_FD;
> - int src_is_phys = src->flags & FUSE_BUF_PHYS_ADDR;
> - int dst_is_phys = src->flags & FUSE_BUF_PHYS_ADDR;
> -
> - if (src_is_phys && !src_is_fd && dst_is_fd) {
> - return fuse_virtio_write(req, dst, dst_off, src, src_off, len);
> - }
> -
> - assert(!src_is_phys && !dst_is_phys);
> - if (!src_is_fd && !dst_is_fd) {
> - void *dstmem = dst->mem + dst_off;
> - void *srcmem = src->mem + src_off;
> + ssize_t res, i, buf_index, iovcnt;
> + struct iovec * iov;
> + int fd = out_buf->buf[0].fd;
> + off_t pos = out_buf->buf[0].pos;
>
> - if (dstmem != srcmem) {
> - if (dstmem + len <= srcmem || srcmem + len <= dstmem)
> - memcpy(dstmem, srcmem, len);
> - else
> - memmove(dstmem, srcmem, len);
> - }
> -
> - return len;
> - } else if (!src_is_fd) {
> - return fuse_buf_write(dst, dst_off, src, src_off, len);
> - } else if (!dst_is_fd) {
> - return fuse_buf_read(dst, dst_off, src, src_off, len);
> - } else if (flags & FUSE_BUF_NO_SPLICE) {
> - return fuse_buf_fd_to_fd(dst, dst_off, src, src_off, len);
> - } else {
> - return fuse_buf_splice(dst, dst_off, src, src_off, len, flags);
> - }
> -}
> -
> -static const struct fuse_buf *fuse_bufvec_current(struct fuse_bufvec *bufv)
> -{
> - if (bufv->idx < bufv->count)
> - return &bufv->buf[bufv->idx];
> + if (in_buf->count > 2)
> + iovcnt = in_buf->count - 1;
> else
> - return NULL;
> -}
> + iovcnt = 1;
>
> -static int fuse_bufvec_advance(struct fuse_bufvec *bufv, size_t len)
> -{
> - const struct fuse_buf *buf = fuse_bufvec_current(bufv);
> + iov = malloc(iovcnt * sizeof(struct iovec));
> + if (!iov)
> + return -ENOMEM;
>
> - bufv->off += len;
> - assert(bufv->off <= buf->size);
> - if (bufv->off == buf->size) {
> - assert(bufv->idx < bufv->count);
> - bufv->idx++;
> - if (bufv->idx == bufv->count)
> - return 0;
> - bufv->off = 0;
> + for (i = 0, buf_index = 1; i < iovcnt; i++, buf_index++) {
> + iov[i].iov_base = in_buf->buf[buf_index].mem;
> + iov[i].iov_len = in_buf->buf[buf_index].size;
> }
> - return 1;
> -}
>
> -ssize_t fuse_buf_copy(fuse_req_t req, struct fuse_bufvec *dstv, struct fuse_bufvec *srcv,
> - enum fuse_buf_copy_flags flags)
> -{
> - size_t copied = 0;
> -
> - if (dstv == srcv)
> - return fuse_buf_size(dstv);
> -
> - for (;;) {
> - const struct fuse_buf *src = fuse_bufvec_current(srcv);
> - const struct fuse_buf *dst = fuse_bufvec_current(dstv);
> - size_t src_len;
> - size_t dst_len;
> - size_t len;
> - ssize_t res;
> -
> - if (src == NULL || dst == NULL)
> - break;
> -
> - src_len = src->size - srcv->off;
> - dst_len = dst->size - dstv->off;
> - len = min_size(src_len, dst_len);
> -
> - res = fuse_buf_copy_one(req, dst, dstv->off, src, srcv->off, len, flags);
> - if (res < 0) {
> - if (!copied)
> - return res;
> - break;
> - }
> - copied += res;
> -
> - if (!fuse_bufvec_advance(srcv, res) ||
> - !fuse_bufvec_advance(dstv, res))
> - break;
> + if (flags & FUSE_BUF_FD_SEEK)
> + res = pwritev(fd, iov, iovcnt, pos);
> + else
> + res = writev(fd, iov, iovcnt);
>
> - if (res < len)
> - break;
> - }
> + if (res == -1 || res == 0)
> + res = -errno;
>
> - return copied;
> + free(iov);
> + return res;
> }
>
> void *fuse_mbuf_iter_advance(struct fuse_mbuf_iter *iter, size_t len)
> diff --git a/contrib/virtiofsd/fuse_common.h b/contrib/virtiofsd/fuse_common.h
> index 001e6d6..c715e52 100644
> --- a/contrib/virtiofsd/fuse_common.h
> +++ b/contrib/virtiofsd/fuse_common.h
> @@ -717,17 +717,18 @@ struct fuse_bufvec {
> size_t fuse_buf_size(const struct fuse_bufvec *bufv);
>
> /**
> - * Copy data from one buffer vector to another
> + * Write data from one buffer vector to another
> *
> * @param req The request this copy is part of
> - * @param dst destination buffer vector
> - * @param src source buffer vector
> + * @param out_buf destination buffer vector
> + * @param in_buf source buffer vector
> * @param flags flags controlling the copy
> - * @return actual number of bytes copied or -errno on error
> + * @return actual number of bytes written or -errno on error
> */
> -ssize_t fuse_buf_copy(fuse_req_t req,
> - struct fuse_bufvec *dst, struct fuse_bufvec *src,
> - enum fuse_buf_copy_flags flags);
> +ssize_t fuse_buf_writev(fuse_req_t req,
> + struct fuse_bufvec *out_buf,
> + struct fuse_bufvec *in_buf,
> + enum fuse_buf_copy_flags flags);
>
> /**
> * Memory buffer iterator
> diff --git a/contrib/virtiofsd/passthrough_ll.c b/contrib/virtiofsd/passthrough_ll.c
> index cc9c175..3082683 100644
> --- a/contrib/virtiofsd/passthrough_ll.c
> +++ b/contrib/virtiofsd/passthrough_ll.c
> @@ -2023,7 +2023,7 @@ static void lo_write_buf(fuse_req_t req, fuse_ino_t ino,
> fuse_debug("lo_write_buf(ino=%" PRIu64 ", size=%zd, off=%lu)\n",
> ino, out_buf.buf[0].size, (unsigned long) off);
>
> - res = fuse_buf_copy(req, &out_buf, in_buf, 0);
> + res = fuse_buf_writev(req, &out_buf, in_buf, out_buf.buf[0].flags);
> if(res < 0) {
> fuse_reply_err(req, -res);
> } else {
> diff --git a/contrib/virtiofsd/seccomp.c b/contrib/virtiofsd/seccomp.c
> index 5f1c873..4bba30b 100644
> --- a/contrib/virtiofsd/seccomp.c
> +++ b/contrib/virtiofsd/seccomp.c
> @@ -60,6 +60,7 @@ static const int syscall_whitelist[] = {
> SCMP_SYS(ppoll),
> SCMP_SYS(prctl), /* TODO restrict to just PR_SET_NAME? */
> SCMP_SYS(preadv),
> + SCMP_SYS(pwritev),
> SCMP_SYS(pwrite64),
> SCMP_SYS(read),
> SCMP_SYS(readlinkat),
> @@ -78,6 +79,7 @@ static const int syscall_whitelist[] = {
> SCMP_SYS(unlinkat),
> SCMP_SYS(utimensat),
> SCMP_SYS(write),
> + SCMP_SYS(writev),
> };
>
> /* Syscalls used when --syslog is enabled */
> --
>
> _______________________________________________
> Virtio-fs mailing list
> Virtio-fs at redhat.com
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--
Dr. David Alan Gilbert / dgilbert at redhat.com / Manchester, UK
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