[Cbe-oss-dev] [PATCH 10/10] spu sched: avoid superflous wakeups inspu_run
장현승
hs8848.jang at samsung.com
Mon Jan 15 17:08:34 EST 2007
The series of patches seems to be a quite good work for better readability.
After applying patches, The patched spu_active() becomes :
int spu_activate(struct spu_context *ctx, unsigned long flags)
{
...
do {
struct spu *spu;
spu = spu_get_idle(ctx);
if (spu) {
spu_bind_context(spu, ctx);
return 0;
}
spu_add_to_rq(ctx);
if (!(flags & SPU_ACTIVATE_NOWAKE))
spu_prio_wait(ctx);
} while (!signal_pending(current));
...
If there is no available spus in spu_get_idle(), the loop will hang forever
because spu_prio_wait() is not called because of SPU_ACTIVATE_NOWAKE propagated from spu_run_init().
Did I miss something?
The description of the patch
"There is no need to directly wake up contexts in spu_activate" is strange
because there was originally no wake-up code but waiting code.
> -----Original Message-----
> From: cbe-oss-dev-bounces+hs8848.jang=samsung.com at ozlabs.org [mailto:cbe-
> oss-dev-bounces+hs8848.jang=samsung.com at ozlabs.org] On Behalf Of Christoph
> Hellwig
> Sent: Monday, January 08, 2007 7:16 AM
> To: cbe-oss-dev at ozlabs.org
> Subject: [Cbe-oss-dev] [PATCH 10/10] spu sched: avoid superflous wakeups
> inspu_run
>
> There is no need to directly wake up contexts in spu_activate when
> called from spu_run, so add a flag to surpress this wakeup.
>
>
> Signed-off-by: Christoph Hellwig <hch at lst.de>
>
> Index: linux-2.6/arch/powerpc/platforms/cell/spufs/spufs.h
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/platforms/cell/spufs/spufs.h 2007-
> 01-07 21:53:39.000000000 +0100
> +++ linux-2.6/arch/powerpc/platforms/cell/spufs/spufs.h 2007-01-07
> 21:53:39.000000000 +0100
> @@ -40,6 +40,11 @@
> struct spu_context_ops;
> struct spu_gang;
>
> +/* ctx->sched_flags */
> +enum {
> + SPU_SCHED_WAKE = 0,
> +};
> +
> struct spu_context {
> struct spu *spu; /* pointer to a physical SPU */
> struct spu_state csa; /* SPU context save area. */
> @@ -76,6 +81,7 @@
>
> /* scheduler fields */
> struct list_head rq;
> + unsigned long sched_flags;
> int prio;
> };
>
> @@ -188,10 +194,13 @@
> void spu_unmap_mappings(struct spu_context *ctx);
>
> void spu_forget(struct spu_context *ctx);
> -int spu_acquire_runnable(struct spu_context *ctx);
> +int spu_acquire_runnable(struct spu_context *ctx, unsigned long flags);
> void spu_acquire_saved(struct spu_context *ctx);
> int spu_acquire_exclusive(struct spu_context *ctx);
> -int spu_activate(struct spu_context *ctx, u64 flags);
> +enum {
> + SPU_ACTIVATE_NOWAKE = 1,
> +};
> +int spu_activate(struct spu_context *ctx, unsigned long flags);
> void spu_deactivate(struct spu_context *ctx);
> void spu_yield(struct spu_context *ctx);
> int __init spu_sched_init(void);
> Index: linux-2.6/arch/powerpc/platforms/cell/spufs/sched.c
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/platforms/cell/spufs/sched.c 2007-
> 01-07 21:53:39.000000000 +0100
> +++ linux-2.6/arch/powerpc/platforms/cell/spufs/sched.c 2007-01-07
> 21:53:39.000000000 +0100
> @@ -261,8 +261,8 @@
> {
> DEFINE_WAIT(wait);
>
> + set_bit(SPU_SCHED_WAKE, &ctx->sched_flags);
> prepare_to_wait_exclusive(&ctx->stop_wq, &wait,
> TASK_INTERRUPTIBLE);
> -
> if (!signal_pending(current)) {
> mutex_unlock(&ctx->state_mutex);
> schedule();
> @@ -270,6 +270,7 @@
> }
> __set_current_state(TASK_RUNNING);
> remove_wait_queue(&ctx->stop_wq, &wait);
> + clear_bit(SPU_SCHED_WAKE, &ctx->sched_flags);
> }
>
> /**
> @@ -289,7 +290,7 @@
> best = sched_find_first_bit(spu_prio->bitmap);
> if (best < MAX_PRIO) {
> struct spu_context *ctx = spu_grab_context(best);
> - if (ctx)
> + if (ctx && test_bit(SPU_SCHED_WAKE, &ctx->sched_flags))
> wake_up(&ctx->stop_wq);
> }
> mutex_unlock(&spu_prio->mutex);
> @@ -329,7 +330,7 @@
> * add the context to the runqueue so it gets woken up once an spu
> * is available.
> */
> -int spu_activate(struct spu_context *ctx, u64 flags)
> +int spu_activate(struct spu_context *ctx, unsigned long flags)
> {
>
> if (ctx->spu)
> @@ -345,7 +346,8 @@
> }
>
> spu_add_to_rq(ctx);
> - spu_prio_wait(ctx);
> + if (!(flags & SPU_ACTIVATE_NOWAKE))
> + spu_prio_wait(ctx);
> } while (!signal_pending(current));
>
>
> Index: linux-2.6/arch/powerpc/platforms/cell/spufs/context.c
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/platforms/cell/spufs/context.c 2007-
> 01-07 21:53:38.000000000 +0100
> +++ linux-2.6/arch/powerpc/platforms/cell/spufs/context.c 2007-01-07
> 21:53:39.000000000 +0100
> @@ -159,7 +159,7 @@
> * Returns 0 and with the context locked on success
> * Returns negative error and with the context _unlocked_ on failure.
> */
> -int spu_acquire_runnable(struct spu_context *ctx)
> +int spu_acquire_runnable(struct spu_context *ctx, unsigned long flags)
> {
> int ret = -EINVAL;
>
> @@ -170,7 +170,7 @@
> */
> if (!ctx->owner)
> goto out_unlock;
> - ret = spu_activate(ctx, 0);
> + ret = spu_activate(ctx, flags);
> if (ret)
> goto out_unlock;
> }
> Index: linux-2.6/arch/powerpc/platforms/cell/spufs/file.c
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/platforms/cell/spufs/file.c 2007-01-04
> 23:14:46.000000000 +0100
> +++ linux-2.6/arch/powerpc/platforms/cell/spufs/file.c 2007-01-07
> 21:53:39.000000000 +0100
> @@ -168,7 +168,7 @@
> if (offset >= ps_size)
> goto out;
>
> - ret = spu_acquire_runnable(ctx);
> + ret = spu_acquire_runnable(ctx, 0);
> if (ret)
> goto out;
>
> @@ -1309,7 +1309,7 @@
> if (ret)
> goto out;
>
> - spu_acquire_runnable(ctx);
> + spu_acquire_runnable(ctx, 0);
> if (file->f_flags & O_NONBLOCK) {
> ret = ctx->ops->send_mfc_command(ctx, &cmd);
> } else {
> Index: linux-2.6/arch/powerpc/platforms/cell/spufs/run.c
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/platforms/cell/spufs/run.c 2007-01-07
> 21:53:36.000000000 +0100
> +++ linux-2.6/arch/powerpc/platforms/cell/spufs/run.c 2007-01-07
> 22:46:07.000000000 +0100
> @@ -143,7 +143,7 @@
> int ret;
> unsigned long runcntl = SPU_RUNCNTL_RUNNABLE;
>
> - ret = spu_acquire_runnable(ctx);
> + ret = spu_acquire_runnable(ctx, SPU_ACTIVATE_NOWAKE);
> if (ret)
> return ret;
>
> @@ -155,7 +155,7 @@
> spu_release(ctx);
> ret = spu_setup_isolated(ctx);
> if (!ret)
> - ret = spu_acquire_runnable(ctx);
> + ret = spu_acquire_runnable(ctx,
> SPU_ACTIVATE_NOWAKE);
> }
>
> /* if userspace has set the runcntrl register (eg, to issue
> an
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