Re: [libvirt-users] dramatic performance slowdown due to THP allocation failure with full pagecache

Thanks for the reply Daniel, However I think you slightly misunderstood the scenario... On 14 November 2017 at 10:32, Daniel P. Berrange <berrange(a)redhat.com&gt; wrote: > IOW, if your application has a certain expectation of performance that can only > be satisfied by having the KVM guest backed by huge pages, then you should > really change to explicitly reserve huge pages for the guests, and not rely on > THP which inherantly can't provide any guarantee in this area. We already do this. The problem is not hugepage backing of the guest, it is THP allocation inside the guest (or indeed on a bare-metal host). The issue in the HPC world is that we support so many different applications (some of which are complete black-boxes) that explicit hugepage allocation for application memory is generally not viable, so we are reliant on THP to avoid TLB thrashing.