On 07/28/20 at 05:15pm, Mike Rapoport wrote: > On Tue, Jul 28, 2020 at 07:02:54PM +0800, Baoquan He wrote: > > On 07/28/20 at 08:11am, Mike Rapoport wrote: > > > From: Mike Rapoport <rppt****@linux*****> > > > > > > numa_clear_kernel_node_hotplug() function first traverses numa_meminfo > > > regions to set node ID in memblock.reserved and than traverses > > > memblock.reserved to update reserved_nodemask to include node IDs that were > > > set in the first loop. > > > > > > Remove redundant traversal over memblock.reserved and update > > > reserved_nodemask while iterating over numa_meminfo. > > > > > > Signed-off-by: Mike Rapoport <rppt****@linux*****> > > > --- > > > arch/x86/mm/numa.c | 26 ++++++++++---------------- > > > 1 file changed, 10 insertions(+), 16 deletions(-) > > > > > > diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c > > > index 8ee952038c80..4078abd33938 100644 > > > --- a/arch/x86/mm/numa.c > > > +++ b/arch/x86/mm/numa.c > > > @@ -498,31 +498,25 @@ static void __init numa_clear_kernel_node_hotplug(void) > > > * and use those ranges to set the nid in memblock.reserved. > > > * This will split up the memblock regions along node > > > * boundaries and will set the node IDs as well. > > > + * > > > + * The nid will also be set in reserved_nodemask which is later > > > + * used to clear MEMBLOCK_HOTPLUG flag. > > > + * > > > + * [ Note, when booting with mem=nn[kMG] or in a kdump kernel, > > > + * numa_meminfo might not include all memblock.reserved > > > + * memory ranges, because quirks such as trim_snb_memory() > > > + * reserve specific pages for Sandy Bridge graphics. > > > + * These ranges will remain with nid == MAX_NUMNODES. ] > > > */ > > > for (i = 0; i < numa_meminfo.nr_blks; i++) { > > > struct numa_memblk *mb = numa_meminfo.blk + i; > > > int ret; > > > > > > ret = memblock_set_node(mb->start, mb->end - mb->start, &memblock.reserved, mb->nid); > > > + node_set(mb->nid, reserved_nodemask); > > > > Really? This will set all node id into reserved_nodemask. But in the > > current code, it's setting nid into memblock reserved region which > > interleaves with numa_memoinfo, then get those nid and set it in > > reserved_nodemask. This is so different, with my understanding. Please > > correct me if I am wrong. > > You are right, I've missed the intersections of numa_meminfo with > memblock.reserved. > > x86 interaction with membock is so, hmm, interesting... Yeah, numa_clear_kernel_node_hotplug() intends to find out any memory node which has reserved memory, then make it as unmovable. Setting all node id into reserved_nodemask will break the use case of hot removing hotpluggable boot memory after system bootup.
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