Re: New NUMA support coming to CURRENT

Hello,

This work has been committed.  It is governed by a new 'NUMA' config 
option and 'DEVICE_NUMA' and 'VM_NUMA_ALLOC' have both been retired.  This 
option is fairly light weight and I will likely enable it in GENERIC 
before 12.0 release.

I have heard reports that switching from a default policy of first-touch 
to round-robin has caused some performance regression.  You can change the 
default policy at runtime by doing the following:

cpuset -s 1 -n first-touch:all

This is the default set that all others inherit from.  You can query the 
current default with:
cpuset -g -s 1

I will be investigating the regression and tweaking the default policy 
based on performance feedback from multiple workloads.  This may take some 
time.

numactl is still functional but deprecated.  Man pages will be updated 
soonish.

Thank you for your patience as I work on refining this somewhat involved 
feature.

Thanks,
Jeff

On Tue, 9 Jan 2018, Jeff Roberson wrote:

> Hello folks,
>
> I am working on merging improved NUMA support with policy implemented by 
> cpuset(2) over the next week.  This work has been supported by Dell/EMC's 
> Isilon product division and Netflix.  You can see some discussion of these 
> changes here:
>
> https://reviews.freebsd.org/D13403
> https://reviews.freebsd.org/D13289
> https://reviews.freebsd.org/D13545
>
> The work has been done in user/jeff/numa if you want to look at svn history 
> or experiment with the branch.  It has been tested by Peter Holm on i386 and 
> amd64 and it has been verified to work on arm at various points.
>
> We are working towards compatibility with libnuma and linux mbind.  These 
> commits will bring in improved support for NUMA in the kernel.  There are new 
> domain specific allocation functions available to kernel for UMA, malloc, 
> kmem_, and vm_page*.  busdmamem consumers will automatically be placed in the 
> correct domain, bringing automatic improvements to some device performance.
>
> cpuset will be able to constrains processes, groups of processes, jails, etc. 
> to subsets of the system memory domains, just as it can with sets of cpus. 
> It can set default policy for any of the above.  Threads can use cpusets to 
> set policy that specifies a subset of their visible domains.
>
> Available policies are first-touch (local in linux terms), round-robin 
> (similar to linux interleave), and preferred.  For now, the default is 
> round-robin.  You can achieve a fixed domain policy by using round-robin with 
> a bitmask of a single domain.  As the scheduler and VM become more 
> sophisticated we may switch the default to first-touch as linux does.
>
> Currently these features are enabled with VM_NUMA_ALLOC and MAXMEMDOM.  It 
> will eventually be NUMA/MAXMEMDOM to match SMP/MAXCPU.  The current NUMA 
> syscalls and VM_NUMA_ALLOC code was 'experimental' and will be deprecated. 
> numactl will continue to be supported although cpuset should be preferred 
> going forward as it supports the full feature set of the new API.
>
> Thank you for your patience as I deal with the inevitable fallout of such 
> sweeping changes.  If you do have bugs, please file them in bugzilla, or 
> reach out to me directly.  I don't always have time to catch up on all of my 
> mailing list mail and regretfully things slip through the cracks when they 
> are not addressed directly to me.
>
> Thanks,
> Jeff
>