From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ua0-f198.google.com (mail-ua0-f198.google.com [209.85.217.198]) by kanga.kvack.org (Postfix) with ESMTP id F10196B0387 for ; Tue, 14 Feb 2017 04:03:16 -0500 (EST) Received: by mail-ua0-f198.google.com with SMTP id f2so88551889uaf.2 for ; Tue, 14 Feb 2017 01:03:16 -0800 (PST) Received: from mail-it0-x22c.google.com (mail-it0-x22c.google.com. [2607:f8b0:4001:c0b::22c]) by mx.google.com with ESMTPS id n202si2177836itn.123.2017.02.14.01.03.16 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 14 Feb 2017 01:03:16 -0800 (PST) Received: by mail-it0-x22c.google.com with SMTP id c7so27352822itd.1 for ; Tue, 14 Feb 2017 01:03:16 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <1487055180-128750-1-git-send-email-zhouxianrong@huawei.com> References: <1486987349-58711-1-git-send-email-zhouxianrong@huawei.com> <1487055180-128750-1-git-send-email-zhouxianrong@huawei.com> From: Ard Biesheuvel Date: Tue, 14 Feb 2017 09:03:15 +0000 Message-ID: Subject: Re: [PATCH] mm: free reserved area's memmap if possiable Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: zhouxianrong@huawei.com 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 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. > 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? 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. > }; > > 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. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org