The Ubuntu-power-systems project

  1. Bug #1781526
  2. Comment #0

Comment 0 for bug 1781526

Revision history for this message
bugproxy (bugproxy) wrote :

== Comment: #0 - JENIFER HOPPER <email address hidden> - 2018-07-12 11:41:50 ==

---Problem Description---
We would like to request the following simple qemu patch be applied because it can provide significant performance improvements for Power9 KVM guests that benefit from 2MB THP usage:

commit 0c1272cc7c72dfe0ef66be8f283cf67c74b58586
osdep: powerpc64 align memory to allow 2MB radix THP page tables

This allows KVM with the Book3S radix MMU mode to take advantage of
THP and install larger pages in the partition scope page tables (the
host translation).

--

For instance, when THP is enabled I measured a 10% throughput improvement with this patch for a full system P9 Radix guest running the SPECjbb2005 workload.

Contact Information = <email address hidden>

---uname output---
Linux perfwsp6 4.15.0-20-generic #21-Ubuntu SMP Tue Apr 24 06:14:44 UTC 2018 ppc64le ppc64le ppc64le GNU/Linux

Machine Type = 8335-GTH

---Debugger---
A debugger is not configured

---Steps to Reproduce---
 Run a workload that benefits from THP usage in a P9 KVM guest.