Re: [PATCH v3 0/5] add persistent huge zero folio support
From: David Hildenbrand <hidden>
Date: 2025-08-11 10:43:11
Also in:
linux-fsdevel, linux-mm, lkml
On 11.08.25 12:36, Kiryl Shutsemau wrote:
On Mon, Aug 11, 2025 at 12:21:23PM +0200, David Hildenbrand wrote:quoted
On 11.08.25 12:17, Kiryl Shutsemau wrote:quoted
On Mon, Aug 11, 2025 at 11:09:24AM +0100, Lorenzo Stoakes wrote:quoted
On Mon, Aug 11, 2025 at 11:07:48AM +0100, Kiryl Shutsemau wrote:quoted
Well, my worry is that 2M can be a high tax for smaller machines. Compile-time might be cleaner, but it has downsides. It is also not clear if these users actually need physical HZP or virtual is enough. Virtual is cheap.The kernel config flag (default =N) literally says don't use unless you have plenty of memory :) So this isn't an issue.Distros use one-config-fits-all approach. Default N doesn't help anything.You'd probably want a way to say "use the persistent huge zero folio if you machine has more than X Gigs". That's all reasonable stuff that can be had on top of this series.We have 'totalram_pages() < (512 << (20 - PAGE_SHIFT))' check in hugepage_init(). It can [be abstracted out and] re-used.
I'll note that e.g., RHEL 10 already has a minimum RAM requirement of 2 GiB. I think for Fedora it's 1 GiB, with the recommendation of having at least 2 GiB. What might be reasonable is having a kconfig option where one (distro) can define the minimum RAM size for the persistent huge zero folio, and then checking against totalram_pages() during boot. But again, I think this is something that goes on top of this series. (it might also be interesting to allow for disabling the persistent huge zero folio through a cmdline option) -- Cheers, David / dhildenb