[PATCH 0/2] Support Armv8.9/v9.4 FEAT_HAFT

[Marc Zyngier]

On Fri, 02 Aug 2024 10:34:56 +0100,
Yicong Yang <yangyicong at huawei.com> wrote:
> 
> From: Yicong Yang <yangyicong at hisilicon.com>
> 
> This series adds basic support for FEAT_HAFT introduced in Armv8.9/v9.4
> and enable ARCH_HAS_NONLEAF_PMD_YOUNG. The latter will be used in
> lru-gen aging. Tested with lru-gen in below steps:
> 1. Generate a 1GiB workingset by `stress-ng --vm 1`. Then hang the task to
>    stop accessing the memory. (AF bit won't be updated)
> 2. try to age the memory by /sys/kernel/debug/lru_gen
> 
> Run above steps with LRU_GEN_NONLEAF_YOUNG(0x4) and not respectively
> (switching by /sys/kernel/mm/lru_gen/enabled). LRU_GEN_NONLEAF_YOUNG
> will clear and test the PMD AF bit on page walking for aging,
> otherwise will clear and test the PTE AF bit for aging. In this case
> LRU_GEN_NONLEAF_YOUNG will improve the efficiency of page scanning
> since pages won't be accessed and we don't need to scan each PTE.

Improve by how much? Can you please publish numbers that demonstrate
the effect of this feature?

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.