[PATCH 11/16] io_uring: batch io_kiocb allocation

[Jens Axboe]

Similarly to how we use the state->ios_left to know how many references
to get to a file, we can use it to allocate the io_kiocb's we need in
bulk.

Signed-off-by: Jens Axboe <ax...@kernel.dk>
---
 fs/io_uring.c | 41 +++++++++++++++++++++++++++++++++++------
 1 file changed, 35 insertions(+), 6 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 11d045f0f799..62778d7ffb8d 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -135,6 +135,13 @@ struct io_submit_state {
        struct list_head req_list;
        unsigned int req_count;
 
+       /*
+        * io_kiocb alloc cache
+        */
+       void *iocbs[IO_IOPOLL_BATCH];
+       unsigned int free_iocbs;
+       unsigned int cur_iocb;
+
        /*
         * File reference cache
         */
@@ -210,15 +217,33 @@ static void io_req_init(struct io_ring_ctx *ctx, struct 
io_kiocb *req)
        req->ki_flags = 0;
 }
 
-static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx)
+static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx,
+                                  struct io_submit_state *state)
 {
        struct io_kiocb *req;
 
-       req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL);
-       if (!req)
-               return NULL;
+       if (!state)
+               req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL);
+       else if (!state->free_iocbs) {
+               size_t size;
+               int ret;
+
+               size = min_t(size_t, state->ios_left, ARRAY_SIZE(state->iocbs));
+               ret = kmem_cache_alloc_bulk(kiocb_cachep, GFP_KERNEL, size,
+                                               state->iocbs);
+               if (ret <= 0)
+                       return ERR_PTR(-ENOMEM);
+               state->free_iocbs = ret - 1;
+               state->cur_iocb = 1;
+               req = state->iocbs[0];
+       } else {
+               req = state->iocbs[state->cur_iocb];
+               state->free_iocbs--;
+               state->cur_iocb++;
+       }
 
-       io_req_init(ctx, req);
+       if (req)
+               io_req_init(ctx, req);
        return req;
 }
 
@@ -773,7 +798,7 @@ static int __io_submit_one(struct io_ring_ctx *ctx,
        if (unlikely(iocb->flags))
                return -EINVAL;
 
-       req = io_get_req(ctx);
+       req = io_get_req(ctx, state);
        if (unlikely(!req))
                return -EAGAIN;
 
@@ -844,6 +869,9 @@ static void io_submit_state_end(struct io_submit_state 
*state)
        if (!list_empty(&state->req_list))
                io_flush_state_reqs(state->ctx, state);
        io_file_put(state, NULL);
+       if (state->free_iocbs)
+               kmem_cache_free_bulk(kiocb_cachep, state->free_iocbs,
+                                       &state->iocbs[state->cur_iocb]);
 }
 
 /*
@@ -855,6 +883,7 @@ static void io_submit_state_start(struct io_submit_state 
*state,
        state->ctx = ctx;
        INIT_LIST_HEAD(&state->req_list);
        state->req_count = 0;
+       state->free_iocbs = 0;
        state->file = NULL;
        state->ios_left = max_ios;
 #ifdef CONFIG_BLOCK
-- 
2.17.1