Hi Barry,
On 2025/7/21 09:02, Barry Song wrote:
On Wed, Jul 16, 2025 at 8:28 AM Gao Xiang <hsiang...@linux.alibaba.com> wrote:
...
... high-order folios can cause side effects on embedded devices
like routers and IoT devices, which still have MiBs of memory (and I
believe this won't change due to their use cases) but they also use
Linux kernel for quite long time. In short, I don't think enabling
large folios for those devices is very useful, let alone limiting
the minimum folio order for them (It would make the filesystem not
suitable any more for those users. At least that is what I never
want to do). And I believe this is different from the current LBS
support to match hardware characteristics or LBS atomic write
requirement.
Given the difficulty of allocating large folios, it's always a good
idea to have order-0 as a fallback. While I agree with your point,
I have a slightly different perspective — enabling large folios for
those devices might be beneficial, but the maximum order should
remain small. I'm referring to "small" large folios.
Yeah, agreed. Having a way to limit the maximum order for those small
devices (rather than disabling it completely) would be helpful. At
least "small" large folios could still provide benefits when memory
pressure is light.
Thanks,
Gao Xiang
Still, even with those, allocation can be difficult — especially
since so many other allocations (which aren't large folios) can cause
fragmentation. So having order-0 as a fallback remains important.
It seems we're missing a mechanism to enable "small" large folios
for files. For anon large folios, we do have sysfs knobs—though they
don’t seem to be universally appreciated. :-)
Thanks
Barry
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