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Re: [Qemu-devel] [PATCH 01/15] qemu coroutine: support bypass mode
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH 01/15] qemu coroutine: support bypass mode |
Date: |
Wed, 30 Jul 2014 15:45:20 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 |
Il 30/07/2014 13:39, Ming Lei ha scritto:
> This patch introduces several APIs for supporting bypass qemu coroutine
> in case of being not necessary and for performance's sake.
No, this is wrong. Dataplane *must* use the same code as non-dataplane,
anything else is a step backwards.
If you want to bypass coroutines, bdrv_aio_readv/writev must detect the
conditions that allow doing that and call the bdrv_aio_readv/writev
directly.
To begin with, have you benchmarked QEMU and can you provide a trace of
*where* the coroutine overhead lies?
Paolo
> Signed-off-by: Ming Lei <address@hidden>
> ---
> include/block/coroutine.h | 8 ++++++++
> include/block/coroutine_int.h | 5 +++++
> qemu-coroutine-lock.c | 4 ++--
> qemu-coroutine.c | 33 +++++++++++++++++++++++++++++++++
> 4 files changed, 48 insertions(+), 2 deletions(-)
>
> diff --git a/include/block/coroutine.h b/include/block/coroutine.h
> index b408f96..46d2642 100644
> --- a/include/block/coroutine.h
> +++ b/include/block/coroutine.h
> @@ -223,4 +223,12 @@ void coroutine_fn co_aio_sleep_ns(AioContext *ctx,
> QEMUClockType type,
> * Note that this function clobbers the handlers for the file descriptor.
> */
> void coroutine_fn yield_until_fd_readable(int fd);
> +
> +/* qemu coroutine bypass APIs */
> +void qemu_coroutine_set_bypass(bool bypass);
> +bool qemu_coroutine_bypassed(Coroutine *self);
> +bool qemu_coroutine_self_bypassed(void);
> +void qemu_coroutine_set_var(void *var);
> +void *qemu_coroutine_get_var(void);
> +
> #endif /* QEMU_COROUTINE_H */
> diff --git a/include/block/coroutine_int.h b/include/block/coroutine_int.h
> index f133d65..106d0b2 100644
> --- a/include/block/coroutine_int.h
> +++ b/include/block/coroutine_int.h
> @@ -39,6 +39,11 @@ struct Coroutine {
> Coroutine *caller;
> QSLIST_ENTRY(Coroutine) pool_next;
>
> + bool bypass;
> +
> + /* only used in bypass mode */
> + void *opaque;
> +
> /* Coroutines that should be woken up when we yield or terminate */
> QTAILQ_HEAD(, Coroutine) co_queue_wakeup;
> QTAILQ_ENTRY(Coroutine) co_queue_next;
> diff --git a/qemu-coroutine-lock.c b/qemu-coroutine-lock.c
> index e4860ae..7c69ff6 100644
> --- a/qemu-coroutine-lock.c
> +++ b/qemu-coroutine-lock.c
> @@ -82,13 +82,13 @@ static bool qemu_co_queue_do_restart(CoQueue *queue, bool
> single)
>
> bool coroutine_fn qemu_co_queue_next(CoQueue *queue)
> {
> - assert(qemu_in_coroutine());
> + assert(qemu_in_coroutine() || qemu_coroutine_self_bypassed());
> return qemu_co_queue_do_restart(queue, true);
> }
>
> void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue)
> {
> - assert(qemu_in_coroutine());
> + assert(qemu_in_coroutine() || qemu_coroutine_self_bypassed());
> qemu_co_queue_do_restart(queue, false);
> }
>
> diff --git a/qemu-coroutine.c b/qemu-coroutine.c
> index 4708521..0597ed9 100644
> --- a/qemu-coroutine.c
> +++ b/qemu-coroutine.c
> @@ -137,3 +137,36 @@ void coroutine_fn qemu_coroutine_yield(void)
> self->caller = NULL;
> coroutine_swap(self, to);
> }
> +
> +void qemu_coroutine_set_bypass(bool bypass)
> +{
> + Coroutine *self = qemu_coroutine_self();
> +
> + self->bypass = bypass;
> +}
> +
> +bool qemu_coroutine_bypassed(Coroutine *self)
> +{
> + return self->bypass;
> +}
> +
> +bool qemu_coroutine_self_bypassed(void)
> +{
> + Coroutine *self = qemu_coroutine_self();
> +
> + return qemu_coroutine_bypassed(self);
> +}
> +
> +void qemu_coroutine_set_var(void *var)
> +{
> + Coroutine *self = qemu_coroutine_self();
> +
> + self->opaque = var;
> +}
> +
> +void *qemu_coroutine_get_var(void)
> +{
> + Coroutine *self = qemu_coroutine_self();
> +
> + return self->opaque;
> +}
>
- [Qemu-devel] [PATCH 00/14] dataplane: optimization and multi virtqueue support, Ming Lei, 2014/07/30
- [Qemu-devel] [PATCH 01/15] qemu coroutine: support bypass mode, Ming Lei, 2014/07/30
- Re: [Qemu-devel] [PATCH 01/15] qemu coroutine: support bypass mode,
Paolo Bonzini <=
- Re: [Qemu-devel] [PATCH 01/15] qemu coroutine: support bypass mode, Ming Lei, 2014/07/30
- Re: [Qemu-devel] [PATCH 01/15] qemu coroutine: support bypass mode, Paolo Bonzini, 2014/07/30
- Re: [Qemu-devel] [PATCH 01/15] qemu coroutine: support bypass mode, Ming Lei, 2014/07/30
- Re: [Qemu-devel] [PATCH 01/15] qemu coroutine: support bypass mode, BenoƮt Canet, 2014/07/31
- Re: [Qemu-devel] [PATCH 01/15] qemu coroutine: support bypass mode, Ming Lei, 2014/07/31
- Re: [Qemu-devel] [PATCH 01/15] qemu coroutine: support bypass mode, Paolo Bonzini, 2014/07/31
- Re: [Qemu-devel] [PATCH 01/15] qemu coroutine: support bypass mode, Ming Lei, 2014/07/31
- Re: [Qemu-devel] [PATCH 01/15] qemu coroutine: support bypass mode, Paolo Bonzini, 2014/07/31
- Re: [Qemu-devel] [PATCH 01/15] qemu coroutine: support bypass mode, Ming Lei, 2014/07/31
- Re: [Qemu-devel] [PATCH 01/15] qemu coroutine: support bypass mode, Ming Lei, 2014/07/31