lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Mon, 30 Mar 2020 13:26:19 +0300 From: Mike Rapoport <rppt@...ux.ibm.com> To: Michal Hocko <mhocko@...nel.org> Cc: Hoan Tran <Hoan@...amperecomputing.com>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, Andrew Morton <akpm@...ux-foundation.org>, Vlastimil Babka <vbabka@...e.cz>, Oscar Salvador <osalvador@...e.de>, Pavel Tatashin <pavel.tatashin@...rosoft.com>, Alexander Duyck <alexander.h.duyck@...ux.intel.com>, Benjamin Herrenschmidt <benh@...nel.crashing.org>, Paul Mackerras <paulus@...ba.org>, Michael Ellerman <mpe@...erman.id.au>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>, "David S. Miller" <davem@...emloft.net>, Heiko Carstens <heiko.carstens@...ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, Christian Borntraeger <borntraeger@...ibm.com>, "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>, linux-arm-kernel@...ts.infradead.org, linux-s390@...r.kernel.org, sparclinux@...r.kernel.org, x86@...nel.org, linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org, lho@...erecomputing.com, mmorana@...erecomputing.com Subject: Re: [PATCH v3 0/5] mm: Enable CONFIG_NODES_SPAN_OTHER_NODES by default for NUMA On Mon, Mar 30, 2020 at 11:58:43AM +0200, Michal Hocko wrote: > On Mon 30-03-20 12:21:27, Mike Rapoport wrote: > > On Mon, Mar 30, 2020 at 09:42:46AM +0200, Michal Hocko wrote: > > > On Sat 28-03-20 11:31:17, Hoan Tran wrote: > > > > In NUMA layout which nodes have memory ranges that span across other nodes, > > > > the mm driver can detect the memory node id incorrectly. > > > > > > > > For example, with layout below > > > > Node 0 address: 0000 xxxx 0000 xxxx > > > > Node 1 address: xxxx 1111 xxxx 1111 > > > > > > > > Note: > > > > - Memory from low to high > > > > - 0/1: Node id > > > > - x: Invalid memory of a node > > > > > > > > When mm probes the memory map, without CONFIG_NODES_SPAN_OTHER_NODES > > > > config, mm only checks the memory validity but not the node id. > > > > Because of that, Node 1 also detects the memory from node 0 as below > > > > when it scans from the start address to the end address of node 1. > > > > > > > > Node 0 address: 0000 xxxx xxxx xxxx > > > > Node 1 address: xxxx 1111 1111 1111 > > > > > > > > This layout could occur on any architecture. Most of them enables > > > > this config by default with CONFIG_NUMA. This patch, by default, enables > > > > CONFIG_NODES_SPAN_OTHER_NODES or uses early_pfn_in_nid() for NUMA. > > > > > > I am not opposed to this at all. It reduces the config space and that is > > > a good thing on its own. The history has shown that meory layout might > > > be really wild wrt NUMA. The config is only used for early_pfn_in_nid > > > which is clearly an overkill. > > > > > > Your description doesn't really explain why this is safe though. The > > > history of this config is somehow messy, though. Mike has tried > > > to remove it a94b3ab7eab4 ("[PATCH] mm: remove arch independent > > > NODES_SPAN_OTHER_NODES") just to be reintroduced by 7516795739bd > > > ("[PATCH] Reintroduce NODES_SPAN_OTHER_NODES for powerpc") without any > > > reasoning what so ever. This doesn't make it really easy see whether > > > reasons for reintroduction are still there. Maybe there are some subtle > > > dependencies. I do not see any TBH but that might be burried deep in an > > > arch specific code. > > > > Well, back then early_pfn_in_nid() was arch-dependant, today everyone > > except ia64 rely on HAVE_MEMBLOCK_NODE_MAP. > > What would it take to make ia64 use HAVE_MEMBLOCK_NODE_MAP? I would > really love to see that thing go away. It is causing problems when > people try to use memblock api. Sorry, my bad, ia64 does not have NODES_SPAN_OTHER_NODES, but it does have HAVE_MEMBLOCK_NODE_MAP. I remember I've tried killing HAVE_MEMBLOCK_NODE_MAP, but I've run into some problems and then I've got distracted. I too would like to have HAVE_MEMBLOCK_NODE_MAP go away, maybe I'll take another look at it. > > So, if the memblock node map > > is correct, that using CONFIG_NUMA instead of CONFIG_NODES_SPAN_OTHER_NODES > > would only mean that early_pfn_in_nid() will cost several cycles more on > > architectures that didn't select CONFIG_NODES_SPAN_OTHER_NODES (i.e. arm64 > > and sh). > > Do we have any idea on how much of an overhead that is? Because this is > per each pfn so it can accumulate a lot! It's O(log(N)) where N is the amount of the memory banks (ie. memblock.memory.cnt) > > Agian, ia64 is an exception here. > > Thanks for the clarification! > -- > Michal Hocko > SUSE Labs -- Sincerely yours, Mike.
Powered by blists - more mailing lists