linux-kernel - Re: [PATCH v2] arm64: Track no early_pgtable

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Date:   Fri, 5 Nov 2021 18:38:52 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Qian Cai <quic_qiancai@...cinc.com>
Cc:     Will Deacon <will@...nel.org>, Mike Rapoport <rppt@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Russell King <linux@...linux.org.uk>,
        kasan-dev@...glegroups.com, linux-arm-kernel@...ts.infradead.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] arm64: Track no early_pgtable_alloc() for kmemleak

On Fri, Nov 05, 2021 at 11:05:09AM -0400, Qian Cai wrote:
> After switched page size from 64KB to 4KB on several arm64 servers here,
> kmemleak starts to run out of early memory pool due to a huge number of
> those early_pgtable_alloc() calls:
> 
>   kmemleak_alloc_phys()
>   memblock_alloc_range_nid()
>   memblock_phys_alloc_range()
>   early_pgtable_alloc()
>   init_pmd()
>   alloc_init_pud()
>   __create_pgd_mapping()
>   __map_memblock()
>   paging_init()
>   setup_arch()
>   start_kernel()
> 
> Increased the default value of DEBUG_KMEMLEAK_MEM_POOL_SIZE by 4 times
> won't be enough for a server with 200GB+ memory. There isn't much
> interesting to check memory leaks for those early page tables and those
> early memory mappings should not reference to other memory. Hence, no
> kmemleak false positives, and we can safely skip tracking those early
> allocations from kmemleak like we did in the commit fed84c785270
> ("mm/memblock.c: skip kmemleak for kasan_init()") without needing to
> introduce complications to automatically scale the value depends on the
> runtime memory size etc. After the patch, the default value of
> DEBUG_KMEMLEAK_MEM_POOL_SIZE becomes sufficient again.
> 
> Signed-off-by: Qian Cai <quic_qiancai@...cinc.com>

Reviewed-by: Catalin Marinas <catalin.marinas@....com>