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Mon, 08 Jul 2024 00:56:23 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHwDhwbAOT2+jYH36rgsrg8H3M7HtgM6YMwgoIpy3dUhj6MLIdOwlXjThJoWDnueuyn7b4vOQ== X-Received: by 2002:a17:906:4556:b0:a77:b8d2:4566 with SMTP id a640c23a62f3a-a77ba72c927mr623125666b.77.1720425383010; Mon, 08 Jul 2024 00:56:23 -0700 (PDT) Received: from [100.81.188.195] ([178.24.249.36]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a77abd2b5e8sm404843766b.26.2024.07.08.00.56.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 08 Jul 2024 00:56:22 -0700 (PDT) Message-ID: Date: Mon, 8 Jul 2024 09:56:21 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 1/3] mm/memblock: introduce a new helper memblock_estimated_nr_free_pages() To: Wei Yang , rppt@kernel.org, akpm@linux-foundation.org, brauner@kernel.org, oleg@redhat.com, mjguzik@gmail.com, tandersen@netflix.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20240708010010.32347-1-richard.weiyang@gmail.com> Content-Language: en-US From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 08.07.24 03:00, Wei Yang wrote: > During bootup, system may need the number of free pages in the whole system > to do some calculation before all pages are freed to buddy system. Usually > this number is get from totalram_pages(). Since we plan to move the free > pages accounting in __free_pages_core(), this value may not represent > total free pages at the early stage, especially when > CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled. > > Instead of using raw memblock api, let's introduce a new helper for user > to get the estimated number of free pages from memblock point of view. > > Signed-off-by: Wei Yang > CC: David Hildenbrand > Reviewed-by: David Hildenbrand > > --- > v4: adjust comment per david's suggestion > --- > include/linux/memblock.h | 1 + > mm/memblock.c | 20 ++++++++++++++++++++ > 2 files changed, 21 insertions(+) > > diff --git a/include/linux/memblock.h b/include/linux/memblock.h > index 40c62aca36ec..7d1c32b3dc12 100644 > --- a/include/linux/memblock.h > +++ b/include/linux/memblock.h > @@ -486,6 +486,7 @@ static inline __init_memblock bool memblock_bottom_up(void) > > phys_addr_t memblock_phys_mem_size(void); > phys_addr_t memblock_reserved_size(void); > +unsigned long memblock_estimated_nr_pages(void); ^ stale name > phys_addr_t memblock_start_of_DRAM(void); > phys_addr_t memblock_end_of_DRAM(void); > void memblock_enforce_memory_limit(phys_addr_t memory_limit); > diff --git a/mm/memblock.c b/mm/memblock.c > index e81fb68f7f88..26162902789f 100644 > --- a/mm/memblock.c > +++ b/mm/memblock.c > @@ -1729,6 +1729,26 @@ phys_addr_t __init_memblock memblock_reserved_size(void) > return memblock.reserved.total_size; > } > > +/** > + * memblock_estimated_nr_free_pages - return estimated number of free pages > + * from memblock point of view > + * > + * During bootup, subsystems might need a rough estimate of the number of free > + * pages in the whole system, before precise numbers are available from the > + * buddy. Especially with CONFIG_DEFERRED_STRUCT_PAGE_INIT, the numbers > + * obtained from the buddy might be very imprecise during bootup. > + * > + * While we can get the estimated number of free pages from memblock, which is > + * good enough for estimation. I'd drop that sentence. Apart form that LGTM -- Cheers, David / dhildenb