io_uring: temporarily disable registered waits

Disable wait argument registration as it'll be replaced with a more
generic feature. We'll still need IORING_ENTER_EXT_ARG_REG parsing
in a few commits

io_uring: temporarily disable registered waits

Disable wait argument registration as it'll be replaced with a more
generic feature. We'll still need IORING_ENTER_EXT_ARG_REG parsing
in a few commits so leave it be.

Signed-off-by: Pavel Begunkov <[email protected]>
Link: https://lore.kernel.org/r/70b1d1d218c41ba77a76d1789c8641dab0b0563e.1731689588.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <[email protected]>

show more ...

io_uring: add support for fixed wait regions

Generally applications have 1 or a few waits of waiting, yet they pass
in a struct io_uring_getevents_arg every time. This needs to get copied
and, in tu

io_uring: add support for fixed wait regions

Generally applications have 1 or a few waits of waiting, yet they pass
in a struct io_uring_getevents_arg every time. This needs to get copied
and, in turn, the timeout value needs to get copied.

Rather than do this for every invocation, allow the application to
register a fixed set of wait regions that can simply be indexed when
asking the kernel to wait on events.

At ring setup time, the application can register a number of these wait
regions and initialize region/index 0 upfront:

struct io_uring_reg_wait *reg;

reg = io_uring_setup_reg_wait(ring, nr_regions, &ret);

/* set timeout and mark as set, sigmask/sigmask_sz as needed */
reg->ts.tv_sec = 0;
reg->ts.tv_nsec = 100000;
reg->flags = IORING_REG_WAIT_TS;

where nr_regions >= 1 && nr_regions <= PAGE_SIZE / sizeof(*reg). The
above initializes index 0, but 63 other regions can be initialized,
if needed. Now, instead of doing:

struct __kernel_timespec timeout = { .tv_nsec = 100000, };

io_uring_submit_and_wait_timeout(ring, &cqe, nr, &t, NULL);

to wait for events for each submit_and_wait, or just wait, operation, it
can just reference the above region at offset 0 and do:

io_uring_submit_and_wait_reg(ring, &cqe, nr, 0);

to achieve the same goal of waiting 100usec without needing to copy
both struct io_uring_getevents_arg (24b) and struct __kernel_timeout
(16b) for each invocation. Struct io_uring_reg_wait looks as follows:

struct io_uring_reg_wait {
struct __kernel_timespec ts;
__u32 min_wait_usec;
__u32 flags;
__u64 sigmask;
__u32 sigmask_sz;
__u32 pad[3];
__u64 pad2[2];
};

embedding the timeout itself in the region, rather than passing it as
a pointer as well. Note that the signal mask is still passed as a
pointer, both for compatability reasons, but also because there doesn't
seem to be a lot of high frequency waits scenarios that involve setting
and resetting the signal mask for each wait.

The application is free to modify any region before a wait call, or it
can use keep multiple regions with different settings to avoid needing to
modify the same one for wait calls. Up to a page size of regions is mapped
by default, allowing PAGE_SIZE / 64 available regions for use.

The registered region must fit within a page. On a 4kb page size system,
that allows for 64 wait regions if a full page is used, as the size of
struct io_uring_reg_wait is 64b. The region registered must be aligned
to io_uring_reg_wait in size. It's valid to register less than 64
entries.

In network performance testing with zero-copy, this reduced the time
spent waiting on the TX side from 3.12% to 0.3% and the RX side from 4.4%
to 0.3%.

Wait regions are fixed for the lifetime of the ring - once registered,
they are persistent until the ring is torn down. The regions support
minimum wait timeout as well as the regular waits.

Signed-off-by: Jens Axboe <[email protected]>

show more ...

io_uring: clean up a type in io_uring_register_get_file()

Originally "fd" was unsigned int but it was changed to int when we pulled
this code into a separate function in commit 0b6d253e084a
("io_uri

io_uring: clean up a type in io_uring_register_get_file()

Originally "fd" was unsigned int but it was changed to int when we pulled
this code into a separate function in commit 0b6d253e084a
("io_uring/register: provide helper to get io_ring_ctx from 'fd'"). This
doesn't really cause a runtime problem because the call to
array_index_nospec() will clamp negative fds to 0 and nothing else uses
the negative values.

Signed-off-by: Dan Carpenter <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

show more ...

io_uring/register: provide helper to get io_ring_ctx from 'fd'

Can be done in one of two ways:

1) Regular file descriptor, just fget()
2) Registered ring, index our own table for that

In preparati

io_uring/register: provide helper to get io_ring_ctx from 'fd'

Can be done in one of two ways:

1) Regular file descriptor, just fget()
2) Registered ring, index our own table for that

In preparation for adding another register use of needing to get a ctx
from a file descriptor, abstract out this helper and use it in the main
register syscall as well.

Signed-off-by: Jens Axboe <[email protected]>

show more ...

io_uring/register: move io_uring_register(2) related code to register.c

Most of this code is basically self contained, move it out of the core
io_uring file to bring a bit more separation to the reg

io_uring/register: move io_uring_register(2) related code to register.c

Most of this code is basically self contained, move it out of the core
io_uring file to bring a bit more separation to the registration related
bits. This moves another ~10% of the code into register.c.

Signed-off-by: Jens Axboe <[email protected]>

show more ...