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io_uring: defer flushing cached reqs 

Awhile there are requests in the allocation cache -- use them, only if
those ended go for the stashed memory in comp.free_list. As list
manipulation are generally heavy and are not good for caches, flush them
all or as much as can in one go.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
[axboe: return success/failure from io_flush_cached_reqs()]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2021-02-10 00:03:23 +00:00 committed by Jens Axboe
parent c5eef2b944
commit e5d1bc0a91
1 changed files with 20 additions and 10 deletions
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30
fs/io_uring.c
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@ -1952,25 +1952,35 @@ static inline void io_req_complete(struct io_kiocb *req, long res)
__io_req_complete(req, 0, res, 0);
}
static bool io_flush_cached_reqs(struct io_submit_state *state)
{
struct io_kiocb *req = NULL;
while (!list_empty(&state->comp.free_list)) {
req = list_first_entry(&state->comp.free_list, struct io_kiocb,
compl.list);
list_del(&req->compl.list);
state->reqs[state->free_reqs++] = req;
if (state->free_reqs == ARRAY_SIZE(state->reqs))
break;
}
return req != NULL;
}
static struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx)
{
struct io_submit_state *state = &ctx->submit_state;
BUILD_BUG_ON(IO_REQ_ALLOC_BATCH > ARRAY_SIZE(state->reqs));
if (!list_empty(&state->comp.free_list)) {
struct io_kiocb *req;
req = list_first_entry(&state->comp.free_list, struct io_kiocb,
compl.list);
list_del(&req->compl.list);
return req;
}
if (!state->free_reqs) {
gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
int ret;
if (io_flush_cached_reqs(state))
goto got_req;
ret = kmem_cache_alloc_bulk(req_cachep, gfp, IO_REQ_ALLOC_BATCH,
state->reqs);
@ -1986,7 +1996,7 @@ static struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx)
}
state->free_reqs = ret;
}
got_req:
state->free_reqs--;
return state->reqs[state->free_reqs];
}