> On Feb 24, 2021, at 5:26 AM, Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote: > > This is a prototype series that introduces a bulk order-0 page allocator > with sunrpc being the first user. The implementation is not particularly > efficient and the intention is to iron out what the semantics of the API > should be. That said, sunrpc was reported to have reduced allocation > latency when refilling a pool. > > As a side-note, while the implementation could be more efficient, it > would require fairly deep surgery in numerous places. The lock scope would > need to be significantly reduced, particularly as vmstat, per-cpu and the > buddy allocator have different locking protocol that overal -- e.g. all > partially depend on irqs being disabled at various points. Secondly, > the core of the allocator deals with single pages where as both the bulk > allocator and per-cpu allocator operate in batches. All of that has to > be reconciled with all the existing users and their constraints (memory > offline, CMA and cpusets being the trickiest). > > In terms of semantics required by new users, my preference is that a pair > of patches be applied -- the first which adds the required semantic to > the bulk allocator and the second which adds the new user. > > Patch 1 of this series is a cleanup to sunrpc, it could be merged > separately but is included here for convenience. > > Patch 2 is the prototype bulk allocator > > Patch 3 is the sunrpc user. Chuck also has a patch which further caches > pages but is not included in this series. It's not directly > related to the bulk allocator and as it caches pages, it might > have other concerns (e.g. does it need a shrinker?) > > This has only been lightly tested on a low-end NFS server. It did not break > but would benefit from an evaluation to see how much, if any, the headline > performance changes. The biggest concern is that a light test case showed > that there are a *lot* of bulk requests for 1 page which gets delegated to > the normal allocator. The same criteria should apply to any other users. > > include/linux/gfp.h | 13 +++++ > mm/page_alloc.c | 113 +++++++++++++++++++++++++++++++++++++++++- > net/sunrpc/svc_xprt.c | 47 ++++++++++++------ > 3 files changed, 157 insertions(+), 16 deletions(-) Hi Mel- Thank you for carrying the torch! -- Chuck Lever
