On Thu, Apr 11, 2013 at 03:49:20PM -0400, Mikulas Patocka wrote: > If the bi_css pointer points to a structure that is shared between > processes, using atomic instruction causes cache line boucing - it doesn't > cost a few instructions, it costs 2-3 hundreds cycles. > > I modified the patch to use new flag BIO_DROP_CGROUP_REFCOUNT to note that > the refcount must be decremented - if the flag is set, refcounts must be > decremented when bio is destroyed, if it is not set, references are > borrowed from upper layer bio. > > It is less bug-prone than the previous patch. If this becomes an actual bottleneck, the right thing to do is making css ref per-cpu. Please stop messing around with refcounting. NACK. -- tejun -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
