On Wed, Nov 30, 2016 at 01:40:34PM +0100, Jesper Dangaard Brouer wrote: > > On Sun, 27 Nov 2016 13:19:54 +0000 Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote: > > [...] > > SLUB has been the default small kernel object allocator for quite some time > > but it is not universally used due to performance concerns and a reliance > > on high-order pages. The high-order concerns has two major components -- > > high-order pages are not always available and high-order page allocations > > potentially contend on the zone->lock. This patch addresses some concerns > > about the zone lock contention by extending the per-cpu page allocator to > > cache high-order pages. The patch makes the following modifications > > > > o New per-cpu lists are added to cache the high-order pages. This increases > > the cache footprint of the per-cpu allocator and overall usage but for > > some workloads, this will be offset by reduced contention on zone->lock. > > This will also help performance of NIC driver that allocator > higher-order pages for their RX-ring queue (and chop it up for MTU). > I do like this patch, even-though I'm working on moving drivers away > from allocation these high-order pages. > > Acked-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx> > Thanks. > [...] > > This is the result from netperf running UDP_STREAM on localhost. It was > > selected on the basis that it is slab-intensive and has been the subject > > of previous SLAB vs SLUB comparisons with the caveat that this is not > > testing between two physical hosts. > > I do like you are using a networking test to benchmark this. Looking at > the results, my initial response is that the improvements are basically > too good to be true. > FWIW, LKP independently measured the boost to be 23% so it's expected there will be different results depending on exact configuration and CPU. > Can you share how you tested this with netperf and the specific netperf > parameters? The mmtests config file used is configs/config-global-dhp__network-netperf-unbound so all details can be extrapolated or reproduced from that. > e.g. > How do you configure the send/recv sizes? Static range of sizes specified in the config file. > Have you pinned netperf and netserver on different CPUs? > No. While it's possible to do a pinned test which helps stability, it also tends to be less reflective of what happens in a variety of workloads so I took the "harder" option. > For localhost testing, when netperf and netserver run on the same CPU, > you observer half the performance, very intuitively. When pinning > netperf and netserver (via e.g. option -T 1,2) you observe the most > stable results. When allowing netperf and netserver to migrate between > CPUs (default setting), the real fun starts and unstable results, > because now the CPU scheduler is also being tested, and my experience > is also more "fun" memory situations occurs, as I guess we are hopping > between more per CPU alloc caches (also affecting the SLUB per CPU usage > pattern). > Yes which is another reason why I used an unbound configuration. I didn't want to get an artificial boost from pinned server/client using the same per-cpu caches. As a side-effect, it may mean that machines with fewer CPUs get a greater boost as there are fewer per-cpu caches being used. > > 2-socket modern machine > > 4.9.0-rc5 4.9.0-rc5 > > vanilla hopcpu-v3 > > The kernel from 4.9.0-rc5-vanilla to 4.9.0-rc5-hopcpu-v3 only contains > this single change right? Yes. -- Mel Gorman SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>