linux/io_uring/notif.c
Pavel Begunkov 8751d15426 io_uring: reduce scheduling due to tw
Every task_work will try to wake the task to be executed, which causes
excessive scheduling and additional overhead. For some tw it's
justified, but others won't do much but post a single CQE.

When a task waits for multiple cqes, every such task_work will wake it
up. Instead, the task may give a hint about how many cqes it waits for,
io_req_local_work_add() will compare against it and skip wake ups
if #cqes + #tw is not enough to satisfy the waiting condition. Task_work
that uses the optimisation should be simple enough and never post more
than one CQE. It's also ignored for non DEFER_TASKRUN rings.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/d2b77e99d1e86624d8a69f7037d764b739dcd225.1680782017.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-04-06 16:23:28 -06:00

87 lines
2.3 KiB
C

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/net.h>
#include <linux/io_uring.h>
#include "io_uring.h"
#include "notif.h"
#include "rsrc.h"
static void io_notif_complete_tw_ext(struct io_kiocb *notif, struct io_tw_state *ts)
{
struct io_notif_data *nd = io_notif_to_data(notif);
struct io_ring_ctx *ctx = notif->ctx;
if (nd->zc_report && (nd->zc_copied || !nd->zc_used))
notif->cqe.res |= IORING_NOTIF_USAGE_ZC_COPIED;
if (nd->account_pages && ctx->user) {
__io_unaccount_mem(ctx->user, nd->account_pages);
nd->account_pages = 0;
}
io_req_task_complete(notif, ts);
}
static void io_tx_ubuf_callback(struct sk_buff *skb, struct ubuf_info *uarg,
bool success)
{
struct io_notif_data *nd = container_of(uarg, struct io_notif_data, uarg);
struct io_kiocb *notif = cmd_to_io_kiocb(nd);
if (refcount_dec_and_test(&uarg->refcnt))
__io_req_task_work_add(notif, IOU_F_TWQ_LAZY_WAKE);
}
static void io_tx_ubuf_callback_ext(struct sk_buff *skb, struct ubuf_info *uarg,
bool success)
{
struct io_notif_data *nd = container_of(uarg, struct io_notif_data, uarg);
if (nd->zc_report) {
if (success && !nd->zc_used && skb)
WRITE_ONCE(nd->zc_used, true);
else if (!success && !nd->zc_copied)
WRITE_ONCE(nd->zc_copied, true);
}
io_tx_ubuf_callback(skb, uarg, success);
}
void io_notif_set_extended(struct io_kiocb *notif)
{
struct io_notif_data *nd = io_notif_to_data(notif);
if (nd->uarg.callback != io_tx_ubuf_callback_ext) {
nd->account_pages = 0;
nd->zc_report = false;
nd->zc_used = false;
nd->zc_copied = false;
nd->uarg.callback = io_tx_ubuf_callback_ext;
notif->io_task_work.func = io_notif_complete_tw_ext;
}
}
struct io_kiocb *io_alloc_notif(struct io_ring_ctx *ctx)
__must_hold(&ctx->uring_lock)
{
struct io_kiocb *notif;
struct io_notif_data *nd;
if (unlikely(!io_alloc_req(ctx, &notif)))
return NULL;
notif->opcode = IORING_OP_NOP;
notif->flags = 0;
notif->file = NULL;
notif->task = current;
io_get_task_refs(1);
notif->rsrc_node = NULL;
notif->io_task_work.func = io_req_task_complete;
nd = io_notif_to_data(notif);
nd->uarg.flags = SKBFL_ZEROCOPY_FRAG | SKBFL_DONT_ORPHAN;
nd->uarg.callback = io_tx_ubuf_callback;
refcount_set(&nd->uarg.refcnt, 1);
return notif;
}