On Thu, Jul 14, 2016 at 03:18:09PM +0200, Peter Zijlstra wrote: > On Wed, Jul 13, 2016 at 10:51:02PM +0200, Peter Zijlstra wrote: > > So, IIRC, the trade-off is a full memory barrier in read_lock and > > read_unlock() vs sync_sched() in write. > > > > Full memory barriers are expensive and while the combined cost might > > well exceed the cost of the sync_sched() it doesn't suffer the latency > > issues. > > > > Not sure if we can frob the two in a single codebase, but I can have a > > poke if Oleg or Paul doesn't beat me to it. > > OK, not too horrible if I say so myself :-) > > The below is a compile tested only first draft so far. I'll go give it > some runtime next.
Doesn't explode if I run: root@ivb-ep:/cgroup# mkdir ponies; for ((i=0; i<60; i++)) ; do while :; do echo $$ > tasks; echo $$ > ponies/tasks ; done & done with cgroup using either READER or WRITER bias. So passes light torture.
