Re: [PATCH v5 0/5] sparse_init rewrite

[Michael Ellerman]

Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> writes:

>> About PPC64, your patchset fixes the issue as the population gets followed by a
>> sparse_init_one_section().
>>
>> It can be seen here:
>>
>> Before:
>>
>> kernel: vmemmap_populate f000000000000000..f000000000004000, node 0
>> kernel:       * f000000000000000..f000000000010000 allocated at (____ptrval____)
>> kernel: vmemmap_populate f000000000000000..f000000000008000, node 0
>> kernel:       * f000000000000000..f000000000010000 allocated at (____ptrval____)
>> kernel: vmemmap_populate f000000000000000..f00000000000c000, node 0
>> kernel:       * f000000000000000..f000000000010000 allocated at (____ptrval____)
>>
>>
>> After:
>>
>> kernel: vmemmap_populate f000000000000000..f000000000004000, node 0
>> kernel:       * f000000000000000..f000000000010000 allocated at (____ptrval____)
>> kernel: vmemmap_populate f000000000000000..f000000000008000, node 0
>> kernel: vmemmap_populate f000000000000000..f00000000000c000, node 0
>> kernel: vmemmap_populate f000000000000000..f000000000010000, node 0
>> kernel: vmemmap_populate f000000000010000..f000000000014000, node 0
>> kernel:       * f000000000010000..f000000000020000 allocated at (____ptrval____)
>>
>>
>> As can be seen, before the patchset, we keep calling vmemmap_create_mapping() even if we
>> populated that section already, because of vmemmap_populated() checking for SECTION_HAS_MEM_MAP.
>>
>> After the patchset, since each population is being followed by a call to sparse_init_one_section(),
>> when vmemmap_populated() gets called, we have SECTION_HAS_MEM_MAP already in case the section
>> was populated.
>
> Hi Oscar,
>
> Right, I also like that this solution removes one extra loop, thus
> reduces the code size. We were populating pages in one place, and then
> loop again to set sections, now we do both in one place, but still
> allow preallocation of memory to reduces fragmentation on all
> platforms. However, I still wanted to see if someone could test on
> real hardware.

I booted it on a small VM and a 160 CPU 4 node machine, both booted
fine.

If you want:
  Tested-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> (powerpc)


Thanks for fixing it up for us.

cheers