Re: [PATCH v2 1/2] mm, swap: speed up hibernation allocation and writeout

[Kairui Song]

On Sun, Feb 15, 2026 at 09:02:36AM +0800, Andrew Morton wrote:
> On Sun, 15 Feb 2026 19:15:05 +0800 Kairui Song via B4 Relay <devnull+kasong.tencent.com@xxxxxxxxxx> wrote:
> 
> > Since commit 0ff67f990bd4 ("mm, swap: remove swap slot cache"),
> > hibernation has been using the swap slot slow allocation path for
> > simplification, which turns out might cause regression for some
> > devices because the allocator now rotates clusters too often, leading to
> > slower allocation and more random distribution of data.
> > 
> > Fast allocation is not complex, so implement hibernation support as
> > well.
> > 
> > And reduce the indent of the code too, while at it. It doesn't have to
> > check the device flag, as the allocator will also check the device flag
> > and refuse to allocate if the device is not writable.
> > 
> > Test result with Samsung SSD 830 Series (SATA II, 3.0 Gbps) shows the
> > performance is several times better [1]:
> > 6.19:               324 seconds
> > After this series:  35 seconds
> 
> 10x is a lot, so I think we should offer this to -stable kernels.
> 
> If you agree, could you please prepare a more backportable fix? 
> Something minimal, separated from the [2/2] cleanup and without the
> incidental whitespace alteration?

Hi Andrew,

I think this is already very close to minimal. But I can send a v3 to
split the indention change in a standalone patch, just to reduce the
LOC changed for stable backport.

I'll also cc stable too. I think we only need to fix for 6.18 and
6.19 right? They will still need manual conflict resolving even
without the indention change. But I can help with that.