* [PATCH] io_uring: reduce/pack size of io_ring_ctx
@ 2019-11-07 20:23 Jens Axboe
2019-11-08 0:00 ` Jackie Liu
0 siblings, 1 reply; 5+ messages in thread
From: Jens Axboe @ 2019-11-07 20:23 UTC (permalink / raw)
To: io-uring
With the recent flurry of additions and changes to io_uring, the
layout of io_ring_ctx has become a bit stale. We're right now at
704 bytes in size on my x86-64 build, or 11 cachelines. This
patch does two things:
- We have to completion structs embedded, that we only use for
quiesce of the ctx (or shutdown) and for sqthread init cases.
That 2x32 bytes right there, let's dynamically allocate them.
- Reorder the struct a bit with an eye on cachelines, use cases,
and holes.
With this patch, we're down to 512 bytes, or 8 cachelines.
Signed-off-by: Jens Axboe <[email protected]>
--
diff --git a/fs/io_uring.c b/fs/io_uring.c
index f8344f95817e..2dbc108fa27b 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -212,25 +212,14 @@ struct io_ring_ctx {
wait_queue_head_t inflight_wait;
} ____cacheline_aligned_in_smp;
+ struct io_rings *rings;
+
/* IO offload */
struct io_wq *io_wq;
struct task_struct *sqo_thread; /* if using sq thread polling */
struct mm_struct *sqo_mm;
wait_queue_head_t sqo_wait;
- struct completion sqo_thread_started;
-
- struct {
- unsigned cached_cq_tail;
- atomic_t cached_cq_overflow;
- unsigned cq_entries;
- unsigned cq_mask;
- struct wait_queue_head cq_wait;
- struct fasync_struct *cq_fasync;
- struct eventfd_ctx *cq_ev_fd;
- atomic_t cq_timeouts;
- } ____cacheline_aligned_in_smp;
-
- struct io_rings *rings;
+ struct completion *sqo_done;
/*
* If used, fixed file set. Writers must ensure that ->refs is dead,
@@ -246,7 +235,22 @@ struct io_ring_ctx {
struct user_struct *user;
- struct completion ctx_done;
+ struct completion *ctx_done;
+
+#if defined(CONFIG_UNIX)
+ struct socket *ring_sock;
+#endif
+
+ struct {
+ unsigned cached_cq_tail;
+ atomic_t cached_cq_overflow;
+ unsigned cq_entries;
+ unsigned cq_mask;
+ struct wait_queue_head cq_wait;
+ struct fasync_struct *cq_fasync;
+ struct eventfd_ctx *cq_ev_fd;
+ atomic_t cq_timeouts;
+ } ____cacheline_aligned_in_smp;
struct {
struct mutex uring_lock;
@@ -268,10 +272,6 @@ struct io_ring_ctx {
spinlock_t inflight_lock;
struct list_head inflight_list;
} ____cacheline_aligned_in_smp;
-
-#if defined(CONFIG_UNIX)
- struct socket *ring_sock;
-#endif
};
struct sqe_submit {
@@ -396,7 +396,7 @@ static void io_ring_ctx_ref_free(struct percpu_ref *ref)
{
struct io_ring_ctx *ctx = container_of(ref, struct io_ring_ctx, refs);
- complete(&ctx->ctx_done);
+ complete(ctx->ctx_done);
}
static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
@@ -407,17 +407,20 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
if (!ctx)
return NULL;
+ ctx->ctx_done = kmalloc(sizeof(struct completion), GFP_KERNEL);
+ ctx->sqo_done = kmalloc(sizeof(struct completion), GFP_KERNEL);
+ if (!ctx->ctx_done || !ctx->sqo_done)
+ goto err;
+
if (percpu_ref_init(&ctx->refs, io_ring_ctx_ref_free,
- PERCPU_REF_ALLOW_REINIT, GFP_KERNEL)) {
- kfree(ctx);
- return NULL;
- }
+ PERCPU_REF_ALLOW_REINIT, GFP_KERNEL))
+ goto err;
ctx->flags = p->flags;
init_waitqueue_head(&ctx->cq_wait);
INIT_LIST_HEAD(&ctx->cq_overflow_list);
- init_completion(&ctx->ctx_done);
- init_completion(&ctx->sqo_thread_started);
+ init_completion(ctx->ctx_done);
+ init_completion(ctx->sqo_done);
mutex_init(&ctx->uring_lock);
init_waitqueue_head(&ctx->wait);
spin_lock_init(&ctx->completion_lock);
@@ -429,6 +432,11 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
spin_lock_init(&ctx->inflight_lock);
INIT_LIST_HEAD(&ctx->inflight_list);
return ctx;
+err:
+ kfree(ctx->ctx_done);
+ kfree(ctx->sqo_done);
+ kfree(ctx);
+ return NULL;
}
static inline bool __io_sequence_defer(struct io_ring_ctx *ctx,
@@ -3037,7 +3045,7 @@ static int io_sq_thread(void *data)
unsigned inflight;
unsigned long timeout;
- complete(&ctx->sqo_thread_started);
+ complete(ctx->sqo_done);
old_fs = get_fs();
set_fs(USER_DS);
@@ -3276,7 +3284,7 @@ static int io_sqe_files_unregister(struct io_ring_ctx *ctx)
static void io_sq_thread_stop(struct io_ring_ctx *ctx)
{
if (ctx->sqo_thread) {
- wait_for_completion(&ctx->sqo_thread_started);
+ wait_for_completion(ctx->sqo_done);
/*
* The park is a bit of a work-around, without it we get
* warning spews on shutdown with SQPOLL set and affinity
@@ -4098,6 +4106,8 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx)
io_unaccount_mem(ctx->user,
ring_pages(ctx->sq_entries, ctx->cq_entries));
free_uid(ctx->user);
+ kfree(ctx->ctx_done);
+ kfree(ctx->sqo_done);
kfree(ctx);
}
@@ -4141,7 +4151,7 @@ static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx)
io_wq_cancel_all(ctx->io_wq);
io_iopoll_reap_events(ctx);
- wait_for_completion(&ctx->ctx_done);
+ wait_for_completion(ctx->ctx_done);
io_ring_ctx_free(ctx);
}
@@ -4545,7 +4555,7 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
* no new references will come in after we've killed the percpu ref.
*/
mutex_unlock(&ctx->uring_lock);
- wait_for_completion(&ctx->ctx_done);
+ wait_for_completion(ctx->ctx_done);
mutex_lock(&ctx->uring_lock);
switch (opcode) {
@@ -4588,7 +4598,7 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
}
/* bring the ctx back to life */
- reinit_completion(&ctx->ctx_done);
+ reinit_completion(ctx->ctx_done);
percpu_ref_reinit(&ctx->refs);
return ret;
}
--
Jens Axboe
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] io_uring: reduce/pack size of io_ring_ctx
2019-11-07 20:23 [PATCH] io_uring: reduce/pack size of io_ring_ctx Jens Axboe
@ 2019-11-08 0:00 ` Jackie Liu
2019-11-08 0:06 ` Jens Axboe
0 siblings, 1 reply; 5+ messages in thread
From: Jackie Liu @ 2019-11-08 0:00 UTC (permalink / raw)
To: Jens Axboe; +Cc: io-uring
> 2019年11月8日 04:23，Jens Axboe <[email protected]> 写道：
>
> With the recent flurry of additions and changes to io_uring, the
> layout of io_ring_ctx has become a bit stale. We're right now at
> 704 bytes in size on my x86-64 build, or 11 cachelines. This
> patch does two things:
>
> - We have to completion structs embedded, that we only use for
> quiesce of the ctx (or shutdown) and for sqthread init cases.
> That 2x32 bytes right there, let's dynamically allocate them.
>
> - Reorder the struct a bit with an eye on cachelines, use cases,
> and holes.
>
> With this patch, we're down to 512 bytes, or 8 cachelines.
>
> Signed-off-by: Jens Axboe <[email protected]>
>
> --
>
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index f8344f95817e..2dbc108fa27b 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -212,25 +212,14 @@ struct io_ring_ctx {
> wait_queue_head_t inflight_wait;
> } ____cacheline_aligned_in_smp;
>
> + struct io_rings *rings;
> +
> /* IO offload */
> struct io_wq *io_wq;
> struct task_struct *sqo_thread; /* if using sq thread polling */
> struct mm_struct *sqo_mm;
> wait_queue_head_t sqo_wait;
> - struct completion sqo_thread_started;
> -
> - struct {
> - unsigned cached_cq_tail;
> - atomic_t cached_cq_overflow;
> - unsigned cq_entries;
> - unsigned cq_mask;
> - struct wait_queue_head cq_wait;
> - struct fasync_struct *cq_fasync;
> - struct eventfd_ctx *cq_ev_fd;
> - atomic_t cq_timeouts;
> - } ____cacheline_aligned_in_smp;
> -
> - struct io_rings *rings;
> + struct completion *sqo_done;
>
> /*
> * If used, fixed file set. Writers must ensure that ->refs is dead,
> @@ -246,7 +235,22 @@ struct io_ring_ctx {
>
> struct user_struct *user;
>
> - struct completion ctx_done;
> + struct completion *ctx_done;
> +
> +#if defined(CONFIG_UNIX)
> + struct socket *ring_sock;
> +#endif
> +
> + struct {
> + unsigned cached_cq_tail;
> + atomic_t cached_cq_overflow;
> + unsigned cq_entries;
> + unsigned cq_mask;
> + struct wait_queue_head cq_wait;
> + struct fasync_struct *cq_fasync;
> + struct eventfd_ctx *cq_ev_fd;
> + atomic_t cq_timeouts;
> + } ____cacheline_aligned_in_smp;
>
> struct {
> struct mutex uring_lock;
> @@ -268,10 +272,6 @@ struct io_ring_ctx {
> spinlock_t inflight_lock;
> struct list_head inflight_list;
> } ____cacheline_aligned_in_smp;
> -
> -#if defined(CONFIG_UNIX)
> - struct socket *ring_sock;
> -#endif
> };
>
> struct sqe_submit {
> @@ -396,7 +396,7 @@ static void io_ring_ctx_ref_free(struct percpu_ref *ref)
> {
> struct io_ring_ctx *ctx = container_of(ref, struct io_ring_ctx, refs);
>
> - complete(&ctx->ctx_done);
> + complete(ctx->ctx_done);
> }
>
> static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
> @@ -407,17 +407,20 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
> if (!ctx)
> return NULL;
>
> + ctx->ctx_done = kmalloc(sizeof(struct completion), GFP_KERNEL);
> + ctx->sqo_done = kmalloc(sizeof(struct completion), GFP_KERNEL);
> + if (!ctx->ctx_done || !ctx->sqo_done)
> + goto err;
> +
> if (percpu_ref_init(&ctx->refs, io_ring_ctx_ref_free,
> - PERCPU_REF_ALLOW_REINIT, GFP_KERNEL)) {
> - kfree(ctx);
> - return NULL;
> - }
> + PERCPU_REF_ALLOW_REINIT, GFP_KERNEL))
> + goto err;
>
> ctx->flags = p->flags;
> init_waitqueue_head(&ctx->cq_wait);
> INIT_LIST_HEAD(&ctx->cq_overflow_list);
> - init_completion(&ctx->ctx_done);
> - init_completion(&ctx->sqo_thread_started);
> + init_completion(ctx->ctx_done);
> + init_completion(ctx->sqo_done);
> mutex_init(&ctx->uring_lock);
> init_waitqueue_head(&ctx->wait);
> spin_lock_init(&ctx->completion_lock);
> @@ -429,6 +432,11 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
> spin_lock_init(&ctx->inflight_lock);
> INIT_LIST_HEAD(&ctx->inflight_list);
> return ctx;
> +err:
> + kfree(ctx->ctx_done);
> + kfree(ctx->sqo_done);
> + kfree(ctx);
> + return NULL;
> }
>
> static inline bool __io_sequence_defer(struct io_ring_ctx *ctx,
> @@ -3037,7 +3045,7 @@ static int io_sq_thread(void *data)
> unsigned inflight;
> unsigned long timeout;
>
> - complete(&ctx->sqo_thread_started);
> + complete(ctx->sqo_done);
>
> old_fs = get_fs();
> set_fs(USER_DS);
> @@ -3276,7 +3284,7 @@ static int io_sqe_files_unregister(struct io_ring_ctx *ctx)
> static void io_sq_thread_stop(struct io_ring_ctx *ctx)
> {
> if (ctx->sqo_thread) {
> - wait_for_completion(&ctx->sqo_thread_started);
> + wait_for_completion(ctx->sqo_done);
> /*
> * The park is a bit of a work-around, without it we get
> * warning spews on shutdown with SQPOLL set and affinity
> @@ -4098,6 +4106,8 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx)
> io_unaccount_mem(ctx->user,
> ring_pages(ctx->sq_entries, ctx->cq_entries));
> free_uid(ctx->user);
> + kfree(ctx->ctx_done);
> + kfree(ctx->sqo_done);
> kfree(ctx);
> }
>
> @@ -4141,7 +4151,7 @@ static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx)
> io_wq_cancel_all(ctx->io_wq);
>
> io_iopoll_reap_events(ctx);
> - wait_for_completion(&ctx->ctx_done);
> + wait_for_completion(ctx->ctx_done);
> io_ring_ctx_free(ctx);
> }
>
> @@ -4545,7 +4555,7 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
> * no new references will come in after we've killed the percpu ref.
> */
> mutex_unlock(&ctx->uring_lock);
> - wait_for_completion(&ctx->ctx_done);
> + wait_for_completion(ctx->ctx_done);
> mutex_lock(&ctx->uring_lock);
>
> switch (opcode) {
> @@ -4588,7 +4598,7 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
> }
>
> /* bring the ctx back to life */
> - reinit_completion(&ctx->ctx_done);
> + reinit_completion(ctx->ctx_done);
> percpu_ref_reinit(&ctx->refs);
> return ret;
> }
This patch looks good, but I prefer sqo_thread_started instead of sqo_done,
because we are marking the thread started, not the end of the thread.
Anyway, Reviewed-by: Jackie Liu <[email protected]>
--
BR, Jackie Liu
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] io_uring: reduce/pack size of io_ring_ctx
2019-11-08 0:00 ` Jackie Liu
@ 2019-11-08 0:06 ` Jens Axboe
2019-11-08 0:35 ` Jens Axboe
0 siblings, 1 reply; 5+ messages in thread
From: Jens Axboe @ 2019-11-08 0:06 UTC (permalink / raw)
To: Jackie Liu; +Cc: io-uring
On 11/7/19 5:00 PM, Jackie Liu wrote:
> This patch looks good, but I prefer sqo_thread_started instead of sqo_done,
> because we are marking the thread started, not the end of the thread.
>
> Anyway, Reviewed-by: Jackie Liu <[email protected]>
Yeah, let's retain the old name. I'll make that change and add your
reviewed-by, thanks.
--
Jens Axboe
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] io_uring: reduce/pack size of io_ring_ctx
2019-11-08 0:06 ` Jens Axboe
@ 2019-11-08 0:35 ` Jens Axboe
2019-11-08 0:43 ` Jackie Liu
0 siblings, 1 reply; 5+ messages in thread
From: Jens Axboe @ 2019-11-08 0:35 UTC (permalink / raw)
To: Jackie Liu; +Cc: io-uring
On 11/7/19 5:06 PM, Jens Axboe wrote:
> On 11/7/19 5:00 PM, Jackie Liu wrote:
>> This patch looks good, but I prefer sqo_thread_started instead of sqo_done,
>> because we are marking the thread started, not the end of the thread.
>>
>> Anyway, Reviewed-by: Jackie Liu <[email protected]>
>
> Yeah, let's retain the old name. I'll make that change and add your
> reviewed-by, thanks.
Actually, would you mind if we just make it ->completions[2] instead?
That saves a kmalloc per ctx setup, I think that's worthwhile enough
to bundle them together:
commit 3b830211e99976650d5da0613dfca105c5007f8b
Author: Jens Axboe <[email protected]>
Date: Thu Nov 7 17:27:39 2019 -0700
io_uring: reduce/pack size of io_ring_ctx
With the recent flurry of additions and changes to io_uring, the
layout of io_ring_ctx has become a bit stale. We're right now at
704 bytes in size on my x86-64 build, or 11 cachelines. This
patch does two things:
- We have to completion structs embedded, that we only use for
quiesce of the ctx (or shutdown) and for sqthread init cases.
That 2x32 bytes right there, let's dynamically allocate them.
- Reorder the struct a bit with an eye on cachelines, use cases,
and holes.
With this patch, we're down to 512 bytes, or 8 cachelines.
Reviewed-by: Jackie Liu <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 4c488bf6e889..2b784262eaff 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -213,24 +213,13 @@ struct io_ring_ctx {
wait_queue_head_t inflight_wait;
} ____cacheline_aligned_in_smp;
+ struct io_rings *rings;
+
/* IO offload */
struct io_wq *io_wq;
struct task_struct *sqo_thread; /* if using sq thread polling */
struct mm_struct *sqo_mm;
wait_queue_head_t sqo_wait;
- struct completion sqo_thread_started;
-
- struct {
- unsigned cached_cq_tail;
- unsigned cq_entries;
- unsigned cq_mask;
- atomic_t cq_timeouts;
- struct wait_queue_head cq_wait;
- struct fasync_struct *cq_fasync;
- struct eventfd_ctx *cq_ev_fd;
- } ____cacheline_aligned_in_smp;
-
- struct io_rings *rings;
/*
* If used, fixed file set. Writers must ensure that ->refs is dead,
@@ -246,7 +235,22 @@ struct io_ring_ctx {
struct user_struct *user;
- struct completion ctx_done;
+ /* 0 is for ctx quiesce/reinit/free, 1 is for sqo_thread started */
+ struct completion *completions;
+
+#if defined(CONFIG_UNIX)
+ struct socket *ring_sock;
+#endif
+
+ struct {
+ unsigned cached_cq_tail;
+ unsigned cq_entries;
+ unsigned cq_mask;
+ atomic_t cq_timeouts;
+ struct wait_queue_head cq_wait;
+ struct fasync_struct *cq_fasync;
+ struct eventfd_ctx *cq_ev_fd;
+ } ____cacheline_aligned_in_smp;
struct {
struct mutex uring_lock;
@@ -268,10 +272,6 @@ struct io_ring_ctx {
spinlock_t inflight_lock;
struct list_head inflight_list;
} ____cacheline_aligned_in_smp;
-
-#if defined(CONFIG_UNIX)
- struct socket *ring_sock;
-#endif
};
struct sqe_submit {
@@ -396,7 +396,7 @@ static void io_ring_ctx_ref_free(struct percpu_ref *ref)
{
struct io_ring_ctx *ctx = container_of(ref, struct io_ring_ctx, refs);
- complete(&ctx->ctx_done);
+ complete(&ctx->completions[0]);
}
static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
@@ -407,17 +407,19 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
if (!ctx)
return NULL;
+ ctx->completions = kmalloc(2 * sizeof(struct completion), GFP_KERNEL);
+ if (!ctx->completions)
+ goto err;
+
if (percpu_ref_init(&ctx->refs, io_ring_ctx_ref_free,
- PERCPU_REF_ALLOW_REINIT, GFP_KERNEL)) {
- kfree(ctx);
- return NULL;
- }
+ PERCPU_REF_ALLOW_REINIT, GFP_KERNEL))
+ goto err;
ctx->flags = p->flags;
init_waitqueue_head(&ctx->cq_wait);
INIT_LIST_HEAD(&ctx->cq_overflow_list);
- init_completion(&ctx->ctx_done);
- init_completion(&ctx->sqo_thread_started);
+ init_completion(&ctx->completions[0]);
+ init_completion(&ctx->completions[1]);
mutex_init(&ctx->uring_lock);
init_waitqueue_head(&ctx->wait);
spin_lock_init(&ctx->completion_lock);
@@ -429,6 +431,10 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
spin_lock_init(&ctx->inflight_lock);
INIT_LIST_HEAD(&ctx->inflight_list);
return ctx;
+err:
+ kfree(ctx->completions);
+ kfree(ctx);
+ return NULL;
}
static inline bool __io_sequence_defer(struct io_ring_ctx *ctx,
@@ -3065,7 +3071,7 @@ static int io_sq_thread(void *data)
unsigned inflight;
unsigned long timeout;
- complete(&ctx->sqo_thread_started);
+ complete(&ctx->completions[1]);
old_fs = get_fs();
set_fs(USER_DS);
@@ -3304,7 +3310,7 @@ static int io_sqe_files_unregister(struct io_ring_ctx *ctx)
static void io_sq_thread_stop(struct io_ring_ctx *ctx)
{
if (ctx->sqo_thread) {
- wait_for_completion(&ctx->sqo_thread_started);
+ wait_for_completion(&ctx->completions[1]);
/*
* The park is a bit of a work-around, without it we get
* warning spews on shutdown with SQPOLL set and affinity
@@ -4126,6 +4132,7 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx)
io_unaccount_mem(ctx->user,
ring_pages(ctx->sq_entries, ctx->cq_entries));
free_uid(ctx->user);
+ kfree(ctx->completions);
kfree(ctx);
}
@@ -4169,7 +4176,7 @@ static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx)
io_wq_cancel_all(ctx->io_wq);
io_iopoll_reap_events(ctx);
- wait_for_completion(&ctx->ctx_done);
+ wait_for_completion(&ctx->completions[0]);
io_ring_ctx_free(ctx);
}
@@ -4573,7 +4580,7 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
* no new references will come in after we've killed the percpu ref.
*/
mutex_unlock(&ctx->uring_lock);
- wait_for_completion(&ctx->ctx_done);
+ wait_for_completion(&ctx->completions[0]);
mutex_lock(&ctx->uring_lock);
switch (opcode) {
@@ -4616,7 +4623,7 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
}
/* bring the ctx back to life */
- reinit_completion(&ctx->ctx_done);
+ reinit_completion(&ctx->completions[0]);
percpu_ref_reinit(&ctx->refs);
return ret;
}
--
Jens Axboe
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] io_uring: reduce/pack size of io_ring_ctx
2019-11-08 0:35 ` Jens Axboe
@ 2019-11-08 0:43 ` Jackie Liu
0 siblings, 0 replies; 5+ messages in thread
From: Jackie Liu @ 2019-11-08 0:43 UTC (permalink / raw)
To: Jens Axboe; +Cc: io-uring
> 2019年11月8日 08:35，Jens Axboe <[email protected]> 写道：
>
> On 11/7/19 5:06 PM, Jens Axboe wrote:
>> On 11/7/19 5:00 PM, Jackie Liu wrote:
>>> This patch looks good, but I prefer sqo_thread_started instead of sqo_done,
>>> because we are marking the thread started, not the end of the thread.
>>>
>>> Anyway, Reviewed-by: Jackie Liu <[email protected]>
>>
>> Yeah, let's retain the old name. I'll make that change and add your
>> reviewed-by, thanks.
>
> Actually, would you mind if we just make it ->completions[2] instead?
> That saves a kmalloc per ctx setup, I think that's worthwhile enough
> to bundle them together:
>
>
> commit 3b830211e99976650d5da0613dfca105c5007f8b
> Author: Jens Axboe <[email protected]>
> Date: Thu Nov 7 17:27:39 2019 -0700
>
> io_uring: reduce/pack size of io_ring_ctx
>
> With the recent flurry of additions and changes to io_uring, the
> layout of io_ring_ctx has become a bit stale. We're right now at
> 704 bytes in size on my x86-64 build, or 11 cachelines. This
> patch does two things:
>
> - We have to completion structs embedded, that we only use for
> quiesce of the ctx (or shutdown) and for sqthread init cases.
> That 2x32 bytes right there, let's dynamically allocate them.
>
> - Reorder the struct a bit with an eye on cachelines, use cases,
> and holes.
>
> With this patch, we're down to 512 bytes, or 8 cachelines.
>
> Reviewed-by: Jackie Liu <[email protected]>
> Signed-off-by: Jens Axboe <[email protected]>
>
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 4c488bf6e889..2b784262eaff 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -213,24 +213,13 @@ struct io_ring_ctx {
> wait_queue_head_t inflight_wait;
> } ____cacheline_aligned_in_smp;
>
> + struct io_rings *rings;
> +
> /* IO offload */
> struct io_wq *io_wq;
> struct task_struct *sqo_thread; /* if using sq thread polling */
> struct mm_struct *sqo_mm;
> wait_queue_head_t sqo_wait;
> - struct completion sqo_thread_started;
> -
> - struct {
> - unsigned cached_cq_tail;
> - unsigned cq_entries;
> - unsigned cq_mask;
> - atomic_t cq_timeouts;
> - struct wait_queue_head cq_wait;
> - struct fasync_struct *cq_fasync;
> - struct eventfd_ctx *cq_ev_fd;
> - } ____cacheline_aligned_in_smp;
> -
> - struct io_rings *rings;
>
> /*
> * If used, fixed file set. Writers must ensure that ->refs is dead,
> @@ -246,7 +235,22 @@ struct io_ring_ctx {
>
> struct user_struct *user;
>
> - struct completion ctx_done;
> + /* 0 is for ctx quiesce/reinit/free, 1 is for sqo_thread started */
> + struct completion *completions;
> +
I think it's okay, it's clear through comments here.
--
BR, Jackie Liu
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2019-11-08 0:43 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
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2019-11-07 20:23 [PATCH] io_uring: reduce/pack size of io_ring_ctx Jens Axboe
2019-11-08 0:00 ` Jackie Liu
2019-11-08 0:06 ` Jens Axboe
2019-11-08 0:35 ` Jens Axboe
2019-11-08 0:43 ` Jackie Liu
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