lkml.org 
[lkml]   [2020]   [Jul]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v5 3/3] mm/page_alloc: Keep memoryless cpuless node 0 offline
* Michal Hocko <mhocko@kernel.org> [2020-07-03 12:59:44]:

> > Honestly, I do not have any idea. I've traced it down to
> > Author: Andi Kleen <ak@suse.de>
> > Date: Tue Jan 11 15:35:48 2005 -0800
> >
> > [PATCH] x86_64: Fix ACPI SRAT NUMA parsing
> >
> > Fix fallout from the recent nodemask_t changes. The node ids assigned
> > in the SRAT parser were off by one.
> >
> > I added a new first_unset_node() function to nodemask.h to allocate
> > IDs sanely.
> >
> > Signed-off-by: Andi Kleen <ak@suse.de>
> > Signed-off-by: Linus Torvalds <torvalds@osdl.org>
> >
> > which doesn't really tell all that much. The historical baggage and a
> > long term behavior which is not really trivial to fix I suspect.
>
> Thinking about this some more, this logic makes some sense afterall.
> Especially in the world without memory hotplug which was very likely the
> case back then. It is much better to have compact node mask rather than
> sparse one. After all node numbers shouldn't really matter as long as
> you have a clear mapping to the HW. I am not sure we export that
> information (except for the kernel ring buffer) though.
>
> The memory hotplug changes that somehow because you can hotremove numa
> nodes and therefore make the nodemask sparse but that is not a common
> case. I am not sure what would happen if a completely new node was added
> and its corresponding node was already used by the renumbered one
> though. It would likely conflate the two I am afraid. But I am not sure
> this is really possible with x86 and a lack of a bug report would
> suggest that nobody is doing that at least.
>

JFYI,
Satheesh copied in this mailchain had opened a bug a year on crash with vcpu
hotplug on memoryless node.

https://bugzilla.kernel.org/show_bug.cgi?id=202187

--
Thanks and Regards
Srikar Dronamraju

\
 
 \ /
  Last update: 2020-07-03 15:09    [W:0.106 / U:0.164 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site