Re: [TECH TOPIC] Reaching consensus on CONFIG_HIGHMEM phaseout

On Mon, Sep 22, 2025, at 19:05, Nicolas Schichan wrote:

quoted

On Fri, Sep 19, 2025, at 16:34, Jason Gunthorpe wrote:

quoted

On Fri, Sep 19, 2025 at 04:22:20PM +0200, Arnd Bergmann wrote:

I did get an email from Nicolas Schichan (added to Cc here),
and he is still supporting a widely deployed Kirkwood based
platform that uses 1GB RAM configurations. He should get
a chance to test that with CONFIG_VMSPLIT_3G_OPT, but I
would expect that to continue working, possibly with minor
bugfixes.

We don't use HIGMEM on our Kirkwood platform, we are happy using a
2G/2G WMSPLIT. We don't need a lot of virtual address space for
userland, and with the 2G split we don't waste physical memory.

Ok, good.

I'm happy to test your patch serie with VMSPLIT_3G_OPT and see if it
still boots with it once you send it.

The patches I did for turning off HIGHMEM on ARMv5 won't have
any effect if you are already running without highmem, so I
don't think we need to wait for your tests specifically.
Any testing would be useful of course just to check that
everything still works.

Jason, I think we can go ahead with your suggestion. I can
post my patches for review once I've done some testing on
them.

     Arnd