Re: API for setting multiple PTEs at once

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Hi Matthew,

On 2/7/23 21:27, Matthew Wilcox wrote:
On Thu, Feb 02, 2023 at 09:14:23PM +0000, Matthew Wilcox wrote:
For those of you not subscribed, linux-mm is currently discussing
how best to handle page faults on large folios.  I simply made it work
when adding large folio support.  Now Yin Fengwei is working on
making it fast.
OK, here's an actual implementation:

https://lore.kernel.org/linux-mm/20230207194937.122543-3-willy@xxxxxxxxxxxxx/

It survives a run of xfstests.  If your architecture doesn't store its
PFNs at PAGE_SHIFT, you're going to want to implement your own set_ptes(),


riscv stores its pfn at PAGE_PFN_SHIFT instead of PAGE_SHIFT, se we need to reimplement set_ptes. But I have been playing with your patchset and we never fall into the case where set_ptes is called with nr > 1, any idea why? I booted a large ubuntu defconfig and launched will_it_scale.page_fault4.

I'll come up with the proper implementation of set_ptes anyway soon.

Thanks,

Alex


or you'll see entirely the wrong pages mapped into userspace.  You may
also wish to implement set_ptes() if it can be done more efficiently
than __pte(pteval(pte) + PAGE_SIZE).

Architectures that implement things like flush_icache_page() and
update_mmu_cache() may want to propose batched versions of those.
That's alpha, csky, m68k, mips, nios2, parisc, sh,
arm, loongarch, openrisc, powerpc, riscv, sparc and xtensa.
Maintainers BCC'd, mailing lists CC'd.

I'm happy to collect implementations and submit them as part of a v6.

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