From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f70.google.com (mail-it0-f70.google.com [209.85.214.70]) by kanga.kvack.org (Postfix) with ESMTP id 87F87680FD0 for ; Tue, 14 Feb 2017 20:53:58 -0500 (EST) Received: by mail-it0-f70.google.com with SMTP id d9so54316984itc.4 for ; Tue, 14 Feb 2017 17:53:58 -0800 (PST) Received: from szxga03-in.huawei.com (szxga03-in.huawei.com. [119.145.14.66]) by mx.google.com with ESMTP id b196si2697387ioa.42.2017.02.14.17.53.56 for ; Tue, 14 Feb 2017 17:53:57 -0800 (PST) Subject: Re: [PATCH] mm: free reserved area's memmap if possiable References: <1486987349-58711-1-git-send-email-zhouxianrong@huawei.com> <1487055180-128750-1-git-send-email-zhouxianrong@huawei.com> From: zhouxianrong Message-ID: <04630153-bc82-ac1f-2f80-344c90200732@huawei.com> Date: Wed, 15 Feb 2017 09:44:25 +0800 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Ard Biesheuvel Cc: "linux-mm@kvack.org" , Mark Rutland , Kefeng Wang , srikar@linux.vnet.ibm.com, Mi.Sophia.Wang@huawei.com, Will Deacon , zhangshiming5@huawei.com, zijun_hu@htc.com, Jisheng Zhang , won.ho.park@huawei.com, Alexander Kuleshov , chengang@emindsoft.com.cn, zhouxiyu@huawei.com, tj@kernel.org, weidu.du@huawei.com, "linux-arm-kernel@lists.infradead.org" , Steve Capper , "linux-kernel@vger.kernel.org" , Joe Perches , Dennis Chen , Andrew Morton , Ganapatrao Kulkarni On 2017/2/14 17:03, Ard Biesheuvel wrote: > On 14 February 2017 at 06:53, wrote: >> From: zhouxianrong >> >> just like freeing no-map area's memmap (gaps of memblock.memory) >> we could free reserved area's memmap (areas of memblock.reserved) >> as well only when user of reserved area indicate that we can do >> this in drivers. that is, user of reserved area know how to >> use the reserved area who could not memblock_free or free_reserved_xxx >> the reserved area and regard the area as raw pfn usage by kernel. >> the patch supply a way to users who want to utilize the memmap >> memory corresponding to raw pfn reserved areas as many as possible. >> users can do this by memblock_mark_raw_pfn interface which mark the >> reserved area as raw pfn and tell free_unused_memmap that this area's >> memmap could be freeed. >> > > Could you give an example how much memory we actually recover by doing > this? I understand it depends on the size of the reserved regions, but > I'm sure you have an actual example that inspired you to write this > patch. i did statistics in our platform, the memmap of reserved region that can be freed is about 6MB. it's fewer. > >> Signed-off-by: zhouxianrong >> --- >> arch/arm64/mm/init.c | 14 +++++++++++++- >> include/linux/memblock.h | 3 +++ >> mm/memblock.c | 24 ++++++++++++++++++++++++ >> 3 files changed, 40 insertions(+), 1 deletion(-) >> >> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c >> index 380ebe7..7e62ef8 100644 >> --- a/arch/arm64/mm/init.c >> +++ b/arch/arm64/mm/init.c >> @@ -358,7 +358,7 @@ static inline void free_memmap(unsigned long start_pfn, unsigned long end_pfn) >> */ >> static void __init free_unused_memmap(void) >> { >> - unsigned long start, prev_end = 0; >> + unsigned long start, end, prev_end = 0; >> struct memblock_region *reg; >> >> for_each_memblock(memory, reg) { >> @@ -391,6 +391,18 @@ static void __init free_unused_memmap(void) >> if (!IS_ALIGNED(prev_end, PAGES_PER_SECTION)) >> free_memmap(prev_end, ALIGN(prev_end, PAGES_PER_SECTION)); >> #endif >> + >> + for_each_memblock(reserved, reg) { >> + if (!(reg->flags & MEMBLOCK_RAW_PFN)) >> + continue; >> + >> + start = memblock_region_memory_base_pfn(reg); >> + end = round_down(memblock_region_memory_end_pfn(reg), >> + MAX_ORDER_NR_PAGES); >> + > > Why are you rounding down end only? Shouldn't you round up start and > round down end? Or does free_memmap() deal with that already? ok, i could round up start. > > In any case, it is good to emphasize that on 4 KB pagesize kernels, we > will only free multiples of 8 MB that are 8 MB aligned, resulting in > 128 KB of memmap backing to be released. > > >> + if (start < end) >> + free_memmap(start, end); >> + } >> } >> #endif /* !CONFIG_SPARSEMEM_VMEMMAP */ >> >> diff --git a/include/linux/memblock.h b/include/linux/memblock.h >> index 5b759c9..9f8d277 100644 >> --- a/include/linux/memblock.h >> +++ b/include/linux/memblock.h >> @@ -26,6 +26,7 @@ enum { >> MEMBLOCK_HOTPLUG = 0x1, /* hotpluggable region */ >> MEMBLOCK_MIRROR = 0x2, /* mirrored region */ >> MEMBLOCK_NOMAP = 0x4, /* don't add to kernel direct mapping */ >> + MEMBLOCK_RAW_PFN = 0x8, /* region whose memmap never be used */ > > I think we should be *very* careful about the combinatorial explosion > that results when combining all these flags, given that this is not a > proper enum but a bit field. > > In any case, the generic memblock change should be in a separate patch > from the arm64 change. MEMBLOCK_RAW_PFN and MEMBLOCK_NOMAP can not be set at the same time > >> }; >> >> struct memblock_region { >> @@ -92,6 +93,8 @@ bool memblock_overlaps_region(struct memblock_type *type, >> int memblock_clear_hotplug(phys_addr_t base, phys_addr_t size); >> int memblock_mark_mirror(phys_addr_t base, phys_addr_t size); >> int memblock_mark_nomap(phys_addr_t base, phys_addr_t size); >> +int memblock_mark_raw_pfn(phys_addr_t base, phys_addr_t size); >> +int memblock_clear_raw_pfn(phys_addr_t base, phys_addr_t size); >> ulong choose_memblock_flags(void); >> >> /* Low level functions */ >> diff --git a/mm/memblock.c b/mm/memblock.c >> index 7608bc3..c103b94 100644 >> --- a/mm/memblock.c >> +++ b/mm/memblock.c >> @@ -814,6 +814,30 @@ int __init_memblock memblock_mark_nomap(phys_addr_t base, phys_addr_t size) >> } >> >> /** >> + * memblock_mark_raw_pfn - Mark raw pfn memory with flag MEMBLOCK_RAW_PFN. >> + * @base: the base phys addr of the region >> + * @size: the size of the region >> + * >> + * Return 0 on succees, -errno on failure. >> + */ >> +int __init_memblock memblock_mark_raw_pfn(phys_addr_t base, phys_addr_t size) >> +{ >> + return memblock_setclr_flag(base, size, 1, MEMBLOCK_RAW_PFN); >> +} >> + >> +/** >> + * memblock_clear_raw_pfn - Clear flag MEMBLOCK_RAW_PFN for a specified region. >> + * @base: the base phys addr of the region >> + * @size: the size of the region >> + * >> + * Return 0 on succees, -errno on failure. >> + */ >> +int __init_memblock memblock_clear_raw_pfn(phys_addr_t base, phys_addr_t size) >> +{ >> + return memblock_setclr_flag(base, size, 0, MEMBLOCK_RAW_PFN); >> +} >> + >> +/** >> * __next_reserved_mem_region - next function for for_each_reserved_region() >> * @idx: pointer to u64 loop variable >> * @out_start: ptr to phys_addr_t for start address of the region, can be %NULL >> -- >> 1.7.9.5 >> >> >> _______________________________________________ >> linux-arm-kernel mailing list >> linux-arm-kernel@lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > . > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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