Re: [PATCH v4 0/2] mm/swap: skip empty clusters in the swapoff scan

[Youngjun Park]

On Wed, Sep 09, 2026 at 10:49:39AM -0700, Andrew Morton wrote:
> On Thu, 10 Sep 2026 01:15:50 +0900 Youngjun Park <youngjun.park@xxxxxxx> wrote:
> 
> > find_next_to_unuse() walks a swap device one offset at a time.  Slot
> > state now lives in a per cluster swap table, so patch 2 dismisses an
> > empty cluster with one counter read instead of SWAPFILE_CLUSTER table
> > reads.
> > 
> > Patch 1 is an unrelated one line comment fix noticed on the way.
> > 
> > A debug test confirmed the skip path runs, and swapoff completed
> > under load with no DEBUG_VM or lockdep splats.
> 
> Please let's try to make the [0/N] words provide a summary of the
> patchset's effects.  The above didn't even tell people that this is a
> swapoff optimization!

Hello Andrew.

I will keep in mind, Thank you for pointing it out.

> I asked an LLM for this summary and we came up with
> 
> :  Speed up swapoff and reduce scanning stalls on large, mostly empty
> :  swap devices by skipping empty clusters.  Reduce swapoff time on a 1
> :  TiB device from 158 ms to 94 ms after filling 128 GiB, and from 392
> :  ms to 73 ms after filling 512 GiB; expect little benefit when
> :  substantial swap data remains.
> 
> Does that sound OK?

Yes, sounds good. summary seems good enough!

Best regards,
Youngjun