Tejun Heo <tj@xxxxxxxxxx> writes: > Even when allocations fail, cfq_find_alloc_queue() always returns a > valid cfq_queue by falling back to the oom cfq_queue. As such, there > isn't much point in taking @gfp_mask and trying "harder" if __GFP_WAIT > is set. GFP_ATOMIC allocations don't fail often and even when they do > the degraded behavior is acceptable and temporary. > > After all, the only reason get_request(), which ultimately determines > the gfp_mask, cares about __GFP_WAIT is to guarantee request > allocation, assuming IO forward progress, for callers which are > willing to wait. There's no reason for cfq_find_alloc_queue() to > behave differently on __GFP_WAIT when it already has a fallback > mechanism. > > Remove @gfp_mask from cfq_find_alloc_queue() and propagate the changes > to its callers. This simplifies the function quite a bit and will > help making async queues per-cfq_group. Sorry, I disagree with this patch. You've changed it so that all cfqq allocations are GFP_ATOMIC, and most, if not all of them simply don't need to be. I'll take it one step further and suggest that we should fix cfq_find_alloc_queue to pass the gfp_mask to check_ioprio_changed. That also shouldn't be using GFP_ATOMIC unconditionally. NAK -Jeff -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
