Re: [PATCH v7 4/6] numa: Introduce and use ram_block_notify_remap()

[David Hildenbrand <david@redhat.com>]

On 04.02.25 18:17, Peter Xu wrote:
> On Sat, Feb 01, 2025 at 09:57:24AM +0000, “William Roche wrote:
>> From: David Hildenbrand <david@redhat.com>
>>
>> Notify registered listeners about the remap at the end of
>> qemu_ram_remap() so e.g., a memory backend can re-apply its
>> settings correctly.
>>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
>> Signed-off-by: William Roche <william.roche@oracle.com>
> 
> IIUC logically speaking we don't need a global remap notifier - here a
> per-ramblock notifier looks more reasonable, like RAMBlock.resized().

Right. Note that qemu_ram_resize() also triggers global notifiers.

> It'll change the notify path from O(N**2) to O(N).  After all, backend1's
> notifier won't care other ramblock's remap() events but only itself's.
> 
> It's not a huge deal as I expect we don't have a huge amount of ramblocks,
> but looks like this series will miss the recent pull anyway..  so let me
> comment as so on this one for consideration when respin.

... and ram remap during reboot is not particularly the fast path we 
care about (or should be caring about).

> 
> We could also merge partial of the series to fix hugetlb poisoning first,
> as this one looks like can be separately done too.

hugetlb frequently uses preallocation, and the remaining patches in this 
series make sure preallocation after remapping happens.

-- 
Cheers,

David / dhildenb