On Mon, Apr 27, 2020 at 05:36:01PM +0200, Christoph Hellwig wrote: > On Sun, Apr 26, 2020 at 10:06:21AM +0800, Ming Lei wrote: > > On Sat, Apr 25, 2020 at 05:48:32PM +0200, Christoph Hellwig wrote: > > > FYI, here is what I think we should be doing (but the memory model > > > experts please correct me): > > > > > > - just drop the direct_issue flag and check for the CPU, which is > > > cheap enough > > > > That isn't correct because the CPU for running async queue may not be > > same with rq->mq_ctx->cpu since hctx->cpumask may include several CPUs > > and we run queue in RR style and it is really a normal case. > > But in that case the memory barrier really doesn't matter anywaẏ. It might be true, however we can save the cost with zero cost, why not do it? Also with document benefit. Thanks, Ming
