On Wed, Sep 01, 2021 at 04:25:01AM +0100, Matthew Wilcox wrote: > On Wed, Sep 01, 2021 at 11:07:41AM +0800, Shijie Huang wrote: > > In the NUMA, we only have one page cache for each file. For the > > program/shared libraries, the > > remote-access delays longer then the local-access. > > > > So, is it possible to implement the per-node page cache for > > programs/libraries? > > At this point, we have no way to support text replication within a > process. So what you're suggesting (if implemented) would work for I created a glibc patch which can do the text replication within a process. I will send to glibc maintainer later.. (it seems glibc does not use patches to maintain the code.) > processes which limit themselves to a single node. That is, if you > have a system with CPUs 0-3 on node 0 and CPUs 4-7 on node 1, a process > which only works on node 0 or only works on node 1 will get text on the > appropriate node. > > If there's a process which runs on both nodes 0 and 1, there's no support > for per-node PGDs. So it will get a mix of pages from nodes 0 and 1, I think we do not need the per-node PGDs. One-PGD for one process is okay to me. > and that doesn't necessarily seem like a big win. I haven't yet dived > into how hard it would be to make mm->pgd a per-node allocation. > > I have been thinking about this a bit; one of our internal performance > teams flagged the potential performance win to me a few months ago. > I don't have a concrete design for text replication yet; there have been > various attempts over the years, but none were particularly compelling. > > By the way, the degree of performance win varies between different CPUs, > but it's measurable on all the systems we've tested on (from three > different vendors). Thank you for sharing this. Thanks Huang Shijie
