Re: [PATCH 10/11] io_uring/rsrc: cache struct io_rsrc_node

Gabriel Krisman Bertazi
2023-03-31T14:09:45Z

Pavel Begunkov <asml.silence@gmail.com> writes:

> Add allocation cache for struct io_rsrc_node, it's always allocated and
> put under ->uring_lock, so it doesn't need any extra synchronisation
> around caches.

Hi Pavel,

I'm curious if you considered using kmem_cache instead of the custom
cache for this case? I'm wondering if this provokes visible difference in
performance in your benchmark.

> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
> include/linux/io_uring_types.h | 1 +
> io_uring/io_uring.c | 11 +++++++++--
> io_uring/rsrc.c | 23 +++++++++++++++--------
> io_uring/rsrc.h | 5 ++++-
> 4 files changed, 29 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
> index 47496059e13a..5d772e36e7fc 100644
> --- a/include/linux/io_uring_types.h
> +++ b/include/linux/io_uring_types.h
> @@ -332,6 +332,7 @@ struct io_ring_ctx {
>
> /* protected by ->uring_lock */
> struct list_head rsrc_ref_list;
> + struct io_alloc_cache rsrc_node_cache;
>
> struct list_head io_buffers_pages;
>
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index 8c3886a4ca96..beedaf403284 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -310,6 +310,7 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
> INIT_LIST_HEAD(&ctx->sqd_list);
> INIT_LIST_HEAD(&ctx->cq_overflow_list);
> INIT_LIST_HEAD(&ctx->io_buffers_cache);
> + io_alloc_cache_init(&ctx->rsrc_node_cache, sizeof(struct io_rsrc_node));
> io_alloc_cache_init(&ctx->apoll_cache, sizeof(struct async_poll));
> io_alloc_cache_init(&ctx->netmsg_cache, sizeof(struct io_async_msghdr));
> init_completion(&ctx->ref_comp);
> @@ -2791,6 +2792,11 @@ static void io_req_caches_free(struct io_ring_ctx *ctx)
> mutex_unlock(&ctx->uring_lock);
> }
>
> +void io_rsrc_node_cache_free(struct io_cache_entry *entry)
> +{
> + kfree(container_of(entry, struct io_rsrc_node, cache));
> +}
> +
> static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
> {
> io_sq_thread_finish(ctx);
> @@ -2816,9 +2822,9 @@ static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
>
> /* there are no registered resources left, nobody uses it */
> if (ctx->rsrc_node)
> - io_rsrc_node_destroy(ctx->rsrc_node);
> + io_rsrc_node_destroy(ctx, ctx->rsrc_node);
> if (ctx->rsrc_backup_node)
> - io_rsrc_node_destroy(ctx->rsrc_backup_node);
> + io_rsrc_node_destroy(ctx, ctx->rsrc_backup_node);
>
> WARN_ON_ONCE(!list_empty(&ctx->rsrc_ref_list));
>
> @@ -2830,6 +2836,7 @@ static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
> #endif
> WARN_ON_ONCE(!list_empty(&ctx->ltimeout_list));
>
> + io_alloc_cache_free(&ctx->rsrc_node_cache, io_rsrc_node_cache_free);
> if (ctx->mm_account) {
> mmdrop(ctx->mm_account);
> ctx->mm_account = NULL;
> diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
> index 0f4e245dee1b..345631091d80 100644
> --- a/io_uring/rsrc.c
> +++ b/io_uring/rsrc.c
> @@ -164,7 +164,7 @@ static void __io_rsrc_put_work(struct io_rsrc_node *ref_node)
> kfree(prsrc);
> }
>
> - io_rsrc_node_destroy(ref_node);
> + io_rsrc_node_destroy(rsrc_data->ctx, ref_node);
> if (atomic_dec_and_test(&rsrc_data->refs))
> complete(&rsrc_data->done);
> }
> @@ -175,9 +175,10 @@ void io_wait_rsrc_data(struct io_rsrc_data *data)
> wait_for_completion(&data->done);
> }
>
> -void io_rsrc_node_destroy(struct io_rsrc_node *ref_node)
> +void io_rsrc_node_destroy(struct io_ring_ctx *ctx, struct io_rsrc_node *node)
> {
> - kfree(ref_node);
> + if (!io_alloc_cache_put(&ctx->rsrc_node_cache, &node->cache))
> + kfree(node);
> }
>
> void io_rsrc_node_ref_zero(struct io_rsrc_node *node)
> @@ -198,13 +199,19 @@ void io_rsrc_node_ref_zero(struct io_rsrc_node *node)
> }
> }
>
> -static struct io_rsrc_node *io_rsrc_node_alloc(void)
> +static struct io_rsrc_node *io_rsrc_node_alloc(struct io_ring_ctx *ctx)
> {
> struct io_rsrc_node *ref_node;
> + struct io_cache_entry *entry;
>
> - ref_node = kzalloc(sizeof(*ref_node), GFP_KERNEL);
> - if (!ref_node)
> - return NULL;
> + entry = io_alloc_cache_get(&ctx->rsrc_node_cache);
> + if (entry) {
> + ref_node = container_of(entry, struct io_rsrc_node, cache);
> + } else {
> + ref_node = kzalloc(sizeof(*ref_node), GFP_KERNEL);
> + if (!ref_node)
> + return NULL;
> + }
>
> ref_node->refs = 1;
> INIT_LIST_HEAD(&ref_node->node);
> @@ -243,7 +250,7 @@ int io_rsrc_node_switch_start(struct io_ring_ctx *ctx)
> {
> if (ctx->rsrc_backup_node)
> return 0;
> - ctx->rsrc_backup_node = io_rsrc_node_alloc();
> + ctx->rsrc_backup_node = io_rsrc_node_alloc(ctx);
> return ctx->rsrc_backup_node ? 0 : -ENOMEM;
> }
>
> diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
> index 17293ab90f64..d1555eaae81a 100644
> --- a/io_uring/rsrc.h
> +++ b/io_uring/rsrc.h
> @@ -4,6 +4,8 @@
>
> #include <net/af_unix.h>
>
> +#include "alloc_cache.h"
> +
> #define IO_RSRC_TAG_TABLE_SHIFT (PAGE_SHIFT - 3)
> #define IO_RSRC_TAG_TABLE_MAX (1U << IO_RSRC_TAG_TABLE_SHIFT)
> #define IO_RSRC_TAG_TABLE_MASK (IO_RSRC_TAG_TABLE_MAX - 1)
> @@ -37,6 +39,7 @@ struct io_rsrc_data {
> };
>
> struct io_rsrc_node {
> + struct io_cache_entry cache;
> int refs;
> struct list_head node;
> struct io_rsrc_data *rsrc_data;
> @@ -65,7 +68,7 @@ void io_rsrc_put_tw(struct callback_head *cb);
> void io_rsrc_node_ref_zero(struct io_rsrc_node *node);
> void io_rsrc_put_work(struct work_struct *work);
> void io_wait_rsrc_data(struct io_rsrc_data *data);
> -void io_rsrc_node_destroy(struct io_rsrc_node *ref_node);
> +void io_rsrc_node_destroy(struct io_ring_ctx *ctx, struct io_rsrc_node *ref_node);
> int io_rsrc_node_switch_start(struct io_ring_ctx *ctx);
> int io_queue_rsrc_removal(struct io_rsrc_data *data, unsigned idx,
> struct io_rsrc_node *node, void *rsrc);

--
Gabriel Krisman Bertazi