Jeff Moyer <jmo...@redhat.com> writes: > Tejun Heo <t...@kernel.org> 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.
It occurs to me that replacing GFP_ATOMIC with GFP_NOWAIT in your patch would address my concerns, and patches 6-8 would apply almost as-is. What do you think about that? -Jeff -- 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/
