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io_uring: optimise read/write iov state storing

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Currently io_read() and io_write() keep separate pointers to an iter and
to struct iov_iter_state, which is not great for register spilling and
requires more on-stack copies. They are both either on-stack or in
req->async_data at the same time, so use struct io_rw_state and keep a
pointer only to it, so having all the state with just one pointer.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/5c5e7ffd7dc25fc35075c70411ba99df72f237fa.1634144845.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2021-10-14 16:10:16 +01:00 committed by Jens Axboe
parent 538941e268
commit c88598a92a
1 changed files with 38 additions and 43 deletions
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81
fs/io_uring.c
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@ -695,9 +695,9 @@ struct io_async_msghdr {
};
struct io_rw_state {
struct iovec fast_iov[UIO_FASTIOV];
struct iov_iter iter;
struct iov_iter_state iter_state;
struct iovec fast_iov[UIO_FASTIOV];
};
struct io_async_rw {
@ -3297,8 +3297,7 @@ static inline bool io_alloc_async_data(struct io_kiocb *req)
}
static int io_setup_async_rw(struct io_kiocb *req, const struct iovec *iovec,
const struct iovec *fast_iov,
struct iov_iter *iter, bool force)
struct io_rw_state *s, bool force)
{
if (!force && !io_op_defs[req->opcode].needs_async_setup)
return 0;
@ -3310,7 +3309,7 @@ static int io_setup_async_rw(struct io_kiocb *req, const struct iovec *iovec,
return -ENOMEM;
}
io_req_map_rw(req, iovec, fast_iov, iter);
io_req_map_rw(req, iovec, s->fast_iov, &s->iter);
iorw = req->async_data;
/* we've copied and mapped the iter, ensure state is saved */
iov_iter_save_state(&iorw->s.iter, &iorw->s.iter_state);
@ -3432,33 +3431,33 @@ static bool need_read_all(struct io_kiocb *req)
static int io_read(struct io_kiocb *req, unsigned int issue_flags)
{
struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
struct io_rw_state __s, *s;
struct iovec *iovec;
struct kiocb *kiocb = &req->rw.kiocb;
struct iov_iter __iter, *iter = &__iter;
bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
struct iov_iter_state __state, *state;
struct io_async_rw *rw;
ssize_t ret, ret2;
if (req_has_async_data(req)) {
rw = req->async_data;
iter = &rw->s.iter;
state = &rw->s.iter_state;
s = &rw->s;
/*
* We come here from an earlier attempt, restore our state to
* match in case it doesn't. It's cheap enough that we don't
* need to make this conditional.
*/
iov_iter_restore(iter, state);
iov_iter_restore(&s->iter, &s->iter_state);
iovec = NULL;
} else {
ret = io_import_iovec(READ, req, &iovec, iter, !force_nonblock);
s = &__s;
iovec = s->fast_iov;
ret = io_import_iovec(READ, req, &iovec, &s->iter, !force_nonblock);
if (ret < 0)
return ret;
state = &__state;
iov_iter_save_state(iter, state);
iov_iter_save_state(&s->iter, &s->iter_state);
}
req->result = iov_iter_count(iter);
req->result = iov_iter_count(&s->iter);
/* Ensure we clear previously set non-block flag */
if (!force_nonblock)
@ -3468,7 +3467,7 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
/* If the file doesn't support async, just async punt */
if (force_nonblock && !io_file_supports_nowait(req, READ)) {
ret = io_setup_async_rw(req, iovec, inline_vecs, iter, true);
ret = io_setup_async_rw(req, iovec, s, true);
return ret ?: -EAGAIN;
}
@ -3478,7 +3477,7 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
return ret;
}
ret = io_iter_do_read(req, iter);
ret = io_iter_do_read(req, &s->iter);
if (ret == -EAGAIN || (req->flags & REQ_F_REISSUE)) {
req->flags &= ~REQ_F_REISSUE;
@ -3502,22 +3501,19 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
* untouched in case of error. Restore it and we'll advance it
* manually if we need to.
*/
iov_iter_restore(iter, state);
iov_iter_restore(&s->iter, &s->iter_state);
ret2 = io_setup_async_rw(req, iovec, inline_vecs, iter, true);
ret2 = io_setup_async_rw(req, iovec, s, true);
if (ret2)
return ret2;
iovec = NULL;
rw = req->async_data;
s = &rw->s;
/*
* Now use our persistent iterator and state, if we aren't already.
* We've restored and mapped the iter to match.
*/
if (iter != &rw->s.iter) {
iter = &rw->s.iter;
state = &rw->s.iter_state;
}
do {
/*
@ -3525,11 +3521,11 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
* above or inside this loop. Advance the iter by the bytes
* that were consumed.
*/
iov_iter_advance(iter, ret);
if (!iov_iter_count(iter))
iov_iter_advance(&s->iter, ret);
if (!iov_iter_count(&s->iter))
break;
rw->bytes_done += ret;
iov_iter_save_state(iter, state);
iov_iter_save_state(&s->iter, &s->iter_state);
/* if we can retry, do so with the callbacks armed */
if (!io_rw_should_retry(req)) {
@ -3543,12 +3539,12 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
* desired page gets unlocked. We can also get a partial read
* here, and if we do, then just retry at the new offset.
*/
ret = io_iter_do_read(req, iter);
ret = io_iter_do_read(req, &s->iter);
if (ret == -EIOCBQUEUED)
return 0;
/* we got some bytes, but not all. retry. */
kiocb->ki_flags &= ~IOCB_WAITQ;
iov_iter_restore(iter, state);
iov_iter_restore(&s->iter, &s->iter_state);
} while (ret > 0);
done:
kiocb_done(kiocb, ret, issue_flags);
@ -3568,28 +3564,27 @@ static int io_write_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
static int io_write(struct io_kiocb *req, unsigned int issue_flags)
{
struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
struct kiocb *kiocb = &req->rw.kiocb;
struct iov_iter __iter, *iter = &__iter;
bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
struct iov_iter_state __state, *state;
struct io_rw_state __s, *s;
struct io_async_rw *rw;
struct iovec *iovec;
struct kiocb *kiocb = &req->rw.kiocb;
bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
ssize_t ret, ret2;
if (req_has_async_data(req)) {
rw = req->async_data;
iter = &rw->s.iter;
state = &rw->s.iter_state;
iov_iter_restore(iter, state);
s = &rw->s;
iov_iter_restore(&s->iter, &s->iter_state);
iovec = NULL;
} else {
ret = io_import_iovec(WRITE, req, &iovec, iter, !force_nonblock);
s = &__s;
iovec = s->fast_iov;
ret = io_import_iovec(WRITE, req, &iovec, &s->iter, !force_nonblock);
if (ret < 0)
return ret;
state = &__state;
iov_iter_save_state(iter, state);
iov_iter_save_state(&s->iter, &s->iter_state);
}
req->result = iov_iter_count(iter);
req->result = iov_iter_count(&s->iter);
/* Ensure we clear previously set non-block flag */
if (!force_nonblock)
@ -3625,9 +3620,9 @@ static int io_write(struct io_kiocb *req, unsigned int issue_flags)
kiocb->ki_flags |= IOCB_WRITE;
if (req->file->f_op->write_iter)
ret2 = call_write_iter(req->file, kiocb, iter);
ret2 = call_write_iter(req->file, kiocb, &s->iter);
else if (req->file->f_op->write)
ret2 = loop_rw_iter(WRITE, req, iter);
ret2 = loop_rw_iter(WRITE, req, &s->iter);
else
ret2 = -EINVAL;
@ -3653,8 +3648,8 @@ static int io_write(struct io_kiocb *req, unsigned int issue_flags)
kiocb_done(kiocb, ret2, issue_flags);
} else {
copy_iov:
iov_iter_restore(iter, state);
ret = io_setup_async_rw(req, iovec, inline_vecs, iter, false);
iov_iter_restore(&s->iter, &s->iter_state);
ret = io_setup_async_rw(req, iovec, s, false);
return ret ?: -EAGAIN;
}
out_free: