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Thu, 05 Nov 2020 00:03:40 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 8EBF6C43387; Thu, 5 Nov 2020 00:03:39 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: sudaraja) by smtp.codeaurora.org (Postfix) with ESMTPSA id 52C2DC433FE; Thu, 5 Nov 2020 00:03:37 +0000 (UTC) MIME-Version: 1.0 Date: Wed, 04 Nov 2020 16:03:36 -0800 From: Sudarshan Rajagopalan To: Will Deacon , Catalin Marinas , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4] arm64/mm: add fallback option to allocate virtually contiguous memory In-Reply-To: References: Message-ID: <4ca1e695f81b368a5487bdaa9b421a95@codeaurora.org> X-Sender: sudaraja@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201105_000347_293342_0E8FDC43 X-CRM114-Status: GOOD ( 23.95 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Gavin Shan , David Hildenbrand , Anshuman Khandual , Steven Price , Andrew Morton , Logan Gunthorpe Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2020-10-16 11:56, Sudarshan Rajagopalan wrote: Hello Will, Catalin, Did you have a chance to review this patch? It is reviewed by others and haven't seen any Nacks. This patch will be useful to have so that memory hotremove doesn't fail when such PMD_SIZE pages aren't available.. which is usually the case in low RAM devices. > When section mappings are enabled, we allocate vmemmap pages from > physically continuous memory of size PMD_SIZE using > vmemmap_alloc_block_buf(). Section mappings are good to reduce TLB > pressure. But when system is highly fragmented and memory blocks are > being hot-added at runtime, its possible that such physically > continuous > memory allocations can fail. Rather than failing the memory hot-add > procedure, add a fallback option to allocate vmemmap pages from > discontinuous pages using vmemmap_populate_basepages(). > > Signed-off-by: Sudarshan Rajagopalan > Reviewed-by: Gavin Shan > Reviewed-by: Anshuman Khandual > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Anshuman Khandual > Cc: Mark Rutland > Cc: Logan Gunthorpe > Cc: David Hildenbrand > Cc: Andrew Morton > Cc: Steven Price > --- > arch/arm64/mm/mmu.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 75df62fea1b6..44486fd0e883 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -1121,8 +1121,11 @@ int __meminit vmemmap_populate(unsigned long > start, unsigned long end, int node, > void *p = NULL; > > p = vmemmap_alloc_block_buf(PMD_SIZE, node, altmap); > - if (!p) > - return -ENOMEM; > + if (!p) { > + if (vmemmap_populate_basepages(addr, next, node, altmap)) > + return -ENOMEM; > + continue; > + } > > pmd_set_huge(pmdp, __pa(p), __pgprot(PROT_SECT_NORMAL)); > } else -- Sudarshan -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel