On Thu, Oct 01, 2015 at 08:37:32AM +0200, Peter Zijlstra wrote:
> On Wed, Sep 30, 2015 at 08:28:41PM +0000, Meyer, Mike wrote:
> > Yes that will also address the issue.
> >
> > The reason I approached the way I did was to avoid adding code path to
> > the far more common uses of {en,de}queue_task() but I doubt anyone is
> > going to notice a difference with the addition of some register
> > save/restores and a compare in that path. Overall the code does
> > shrink with the alternative which is good.
>
> In most cases the flags should be compile time constants, and with the
> inline we can determine the branch at compile time, avoiding emitting
> that branch instruction entirely.
>
> But let me double check the asm for a few important sites.
It looks like the sites in the wakeup path do indeed not get any
additional conditionals.
> > My only comment is I am not sure about the naming of the flag
> > ENQUEUE_TEMP which implies (to me) the enqueue is temporary which
> > clearly it isn't. Maybe something like DEQUEUE_MOVE/ENQUEUE_MOVE
> > would be a bit more descriptive of the use case.
>
> Yes, I ran out of creative juices, let me attempt a better name once
> I've woken up a bit.
How about DEQUEUE_SAVE, ENQUEUE_RESTORE ? Ideally I'd wrap the whole
pattern into a helper but C isn't really supportive of pre+post patterns
like this.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
