Re: [PATCH v3 00/15] Allocate and free frozen pages

[Vlastimil Babka <vbabka@suse.cz>]

On 11/26/24 06:04, Hyeonggon Yoo wrote:
> On Tue, Nov 26, 2024 at 7:38 AM Matthew Wilcox (Oracle)
> <willy@infradead.org> wrote:
>>
>> Slab does not need to use the page refcount at all, and it can avoid
>> an atomic operation on page free.  Hugetlb wants to delay setting the
>> refcount until it has assembled a complete gigantic page. We already
>> have the ability to freeze a page (safely reduce its reference count to
>> 0), so this patchset adds APIs to allocate and free pages which are in
>> a frozen state.
> 
> [+Cc Vlastimil]
> 
> I think with this patchset, we can finally remove the memory barriers used
> in isolate_movable_page(), alloc_slab_page(), and __free_slab(),
> because folio_get_nontail_page() should fail for frozen pages?

Thanks for the heads-up!

> for reference, the patch that introduced the memory barrier:
> https://lore.kernel.org/linux-mm/Y20BRJmRzRVMzoJw@hyeyoo

Are you going to sent the necessary patch on top of this series then? :) We
could route it via -mm to avoid waiting a cycle or needing extra
synchronization. It's not a pure slab change anyway...

Thanks,
Vlastimil

> Best,
> Hyeonggon