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Message-ID: <20200817080405.GL969206@linux.ibm.com>
Date: Mon, 17 Aug 2020 11:04:05 +0300
From: Mike Rapoport <rppt@...ux.ibm.com>
To: Wei Li <liwei213@...wei.com>
Cc: catalin.marinas@....com, will@...nel.org,
saberlily.xia@...ilicon.com, puck.chen@...ilicon.com,
butao@...ilicon.com, fengbaopeng2@...ilicon.com,
nsaenzjulienne@...e.de, steve.capper@....com,
song.bao.hua@...ilicon.com, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, sujunfei2@...ilicon.com
Subject: Re: [PATCH v2] arm64: mm: free unused memmap for sparse memory model
that define VMEMMAP
On Wed, Aug 12, 2020 at 09:06:55AM +0800, Wei Li wrote:
> For the memory hole, sparse memory model that define SPARSEMEM_VMEMMAP
> do not free the reserved memory for the page map, this patch do it.
I've been thinking about it a bit more and it seems that instead of
freeing unused memory map it would be better to allocate the exact
memory map from the beginning.
In sparse_init_nid() we can replace PAGES_PER_SECTION parameter to
__populate_section_memmap() with the calculated value for architectures
that define HAVE_ARCH_PFN_VALID.
Than, I beleive it would be possible to remove free_unused_memmap() in
arm64 and probably in arm32 as well.
> Signed-off-by: Wei Li <liwei213@...wei.com>
> Signed-off-by: Chen Feng <puck.chen@...ilicon.com>
> Signed-off-by: Xia Qing <saberlily.xia@...ilicon.com>
>
> v2: fix the patch v1 compile errors that are not based on the latest mainline.
> ---
> arch/arm64/mm/init.c | 81 +++++++++++++++++++++++++++++++++++++++++++++-------
> 1 file changed, 71 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 1e93cfc7c47a..600889945cd0 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -441,7 +441,48 @@ void __init bootmem_init(void)
> memblock_dump_all();
> }
>
> -#ifndef CONFIG_SPARSEMEM_VMEMMAP
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> +#define VMEMMAP_PAGE_INUSE 0xFD
> +static inline void free_memmap(unsigned long start_pfn, unsigned long end_pfn)
> +{
> + unsigned long addr, end;
> + unsigned long next;
> + pmd_t *pmd;
> + void *page_addr;
> + phys_addr_t phys_addr;
> +
> + addr = (unsigned long)pfn_to_page(start_pfn);
> + end = (unsigned long)pfn_to_page(end_pfn);
> +
> + pmd = pmd_off_k(addr);
> + for (; addr < end; addr = next, pmd++) {
> + next = pmd_addr_end(addr, end);
> +
> + if (!pmd_present(*pmd))
> + continue;
> +
> + if (IS_ALIGNED(addr, PMD_SIZE) &&
> + IS_ALIGNED(next, PMD_SIZE)) {
> + phys_addr = __pfn_to_phys(pmd_pfn(*pmd));
> + memblock_free(phys_addr, PMD_SIZE);
> + pmd_clear(pmd);
> + } else {
> + /* If here, we are freeing vmemmap pages. */
> + memset((void *)addr, VMEMMAP_PAGE_INUSE, next - addr);
> + page_addr = page_address(pmd_page(*pmd));
> +
> + if (!memchr_inv(page_addr, VMEMMAP_PAGE_INUSE,
> + PMD_SIZE)) {
> + phys_addr = __pfn_to_phys(pmd_pfn(*pmd));
> + memblock_free(phys_addr, PMD_SIZE);
> + pmd_clear(pmd);
> + }
> + }
> + }
> +
> + flush_tlb_all();
> +}
> +#else
> static inline void free_memmap(unsigned long start_pfn, unsigned long end_pfn)
> {
> struct page *start_pg, *end_pg;
> @@ -468,31 +509,53 @@ static inline void free_memmap(unsigned long start_pfn, unsigned long end_pfn)
> memblock_free(pg, pgend - pg);
> }
>
> +#endif
> +
> /*
> * The mem_map array can get very big. Free the unused area of the memory map.
> */
> static void __init free_unused_memmap(void)
> {
> - unsigned long start, prev_end = 0;
> + unsigned long start, cur_start, prev_end = 0;
> struct memblock_region *reg;
>
> for_each_memblock(memory, reg) {
> - start = __phys_to_pfn(reg->base);
> + cur_start = __phys_to_pfn(reg->base);
>
> #ifdef CONFIG_SPARSEMEM
> /*
> * Take care not to free memmap entries that don't exist due
> * to SPARSEMEM sections which aren't present.
> */
> - start = min(start, ALIGN(prev_end, PAGES_PER_SECTION));
> -#endif
> + start = min(cur_start, ALIGN(prev_end, PAGES_PER_SECTION));
> +
> /*
> - * If we had a previous bank, and there is a space between the
> - * current bank and the previous, free it.
> + * Free memory in the case of:
> + * 1. if cur_start - prev_end <= PAGES_PER_SECTION,
> + * free pre_end ~ cur_start.
> + * 2. if cur_start - prev_end > PAGES_PER_SECTION,
> + * free pre_end ~ ALIGN(prev_end, PAGES_PER_SECTION).
> */
> if (prev_end && prev_end < start)
> free_memmap(prev_end, start);
>
> + /*
> + * Free memory in the case of:
> + * if cur_start - prev_end > PAGES_PER_SECTION,
> + * free ALIGN_DOWN(cur_start, PAGES_PER_SECTION) ~ cur_start.
> + */
> + if (cur_start > start &&
> + !IS_ALIGNED(cur_start, PAGES_PER_SECTION))
> + free_memmap(ALIGN_DOWN(cur_start, PAGES_PER_SECTION),
> + cur_start);
> +#else
> + /*
> + * If we had a previous bank, and there is a space between the
> + * current bank and the previous, free it.
> + */
> + if (prev_end && prev_end < cur_start)
> + free_memmap(prev_end, cur_start);
> +#endif
> /*
> * Align up here since the VM subsystem insists that the
> * memmap entries are valid from the bank end aligned to
> @@ -507,7 +570,6 @@ static void __init free_unused_memmap(void)
> free_memmap(prev_end, ALIGN(prev_end, PAGES_PER_SECTION));
> #endif
> }
> -#endif /* !CONFIG_SPARSEMEM_VMEMMAP */
>
> /*
> * mem_init() marks the free areas in the mem_map and tells us how much memory
> @@ -524,9 +586,8 @@ void __init mem_init(void)
>
> set_max_mapnr(max_pfn - PHYS_PFN_OFFSET);
>
> -#ifndef CONFIG_SPARSEMEM_VMEMMAP
> free_unused_memmap();
> -#endif
> +
> /* this will put all unused low memory onto the freelists */
> memblock_free_all();
>
> --
> 2.15.0
>
--
Sincerely yours,
Mike.
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