Re: [PATCH v3] mm: hugetlb: optionally allocate gigantic hugepages using cma

From: Qian Cai
Date: Thu Mar 12 2020 - 09:33:25 EST

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In reply to: Roman Gushchin: "[PATCH v3] mm: hugetlb: optionally allocate gigantic hugepages using cma 65;5803;1c Commit 944d9fec8d7a ("hugetlb: add support for gigantic page allocation at runtime") has added the run-time allocation of gigantic pages. However it actually works only at early stages of the system loading, when the majority of memory is free. After some time the memory gets fragmented by non-movable pages, so the chances to find a contiguous 1 GB block are getting close to zero. Even dropping caches manually doesn't help a lot."
Next in thread: Roman Gushchin: "Re: [PATCH v3] mm: hugetlb: optionally allocate gigantic hugepages using cma"
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On Wed, 2020-03-11 at 15:09 -0700, Roman Gushchin wrote:
> +#ifdef CONFIG_CMA
> +static unsigned long hugetlb_cma_size __initdata;
> +
> +static int __init cmdline_parse_hugetlb_cma(char *p)
> +{
> + unsigned long long val;
> + char *endptr;
> +
> + if (!p)
> + return -EINVAL;
> +
> + val = simple_strtoull(p, &endptr, 0);
> + hugetlb_cma_size = memparse(p, &p);
> + return 0;
> +}
> +

Here will generate a compilation warning,

mm/hugetlb.c: In function 'cmdline_parse_hugetlb_cma':
mm/hugetlb.c:5548:21: warning: variable 'val' set but not used [-Wunused-but-
set-variable]
Â unsigned long long val;
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ^~~
Also, the comments for simple_strtoull() in lib/vsprintf.c said,

"This function is obsolete. Please use kstrtoull instead."