On Fri, 18 Oct, at 01:54:49PM, Mel Gorman wrote: > On Fri, Oct 18, 2019 at 12:58:49PM +0100, Matt Fleming wrote: > > On Fri, 18 Oct, at 11:56:03AM, Mel Gorman wrote: > > > A private report stated that system CPU usage was excessive on an AMD > > > EPYC 2 machine while building kernels with much longer build times than > > > expected. The issue is partially explained by high zone lock contention > > > due to the per-cpu page allocator batch and high limits being calculated > > > incorrectly. This series addresses a large chunk of the problem. Patch 1 > > > is mostly cosmetic but prepares for patch 2 which is the real fix. Patch > > > 3 is definiely cosmetic but was noticed while implementing the fix. Proper > > > details are in the changelog for patch 2. > > > > > > include/linux/mm.h | 3 --- > > > mm/internal.h | 3 +++ > > > mm/page_alloc.c | 33 ++++++++++++++++++++------------- > > > 3 files changed, 23 insertions(+), 16 deletions(-) > > > > Just to confirm, these patches don't fix the issue we're seeing on the > > EPYC 2 machines, but they do return the batch sizes to sensible values. > > To be clear, does the patch a) fix *some* of the issue and there is > something else also going on that needs to be chased down or b) has no > impact on build time or system CPU usage on your machine? Sorry, I realise my email was pretty unclear. These patches *do* fix some of the issue because I no longer see as much contention on the zone locks with the patches applied.
