| Date | Mon, 10 Jan 2022 23:49:32 +0900 | From | Alexey Avramov <> | Subject | Re: [PATCH v6 0/9] Multigenerational LRU Framework |
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Note that with vm.swappiness=0, the vm.watermark_scale_factor value does not affect the swap possibility: MGLRU ignores sc->file_is_tiny.
With the classic 2-gen LRU swapping goes well at swappiness=0 and high vm.watermark_scale_factor, which is expected according to the documentation: "At 0, the kernel will not initiate swap until the amount of free and file-backed pages is less than the high watermark in a zone." [1]
With vm.swappiness=0, no swap occurs with any vm.watermark_scale_factor value with MGLRU.
I used to see in practice (with MGLRU v3) the impossibility of swapping when vm.swappiness=0 and vm.watermark_scale_factor=1000.
At a minimum, this will require updating the documentation for vm.swappiness.
BTW, why MGLRU doesn't use something like sc->file_is_tiny?
[1] https://github.com/torvalds/linux/blob/v5.16/Documentation/admin-guide/sysctl/vm.rst#swappiness
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