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From: Srikar Dronamraju <firstname.lastname@example.org> To: Vlastimil Babka <email@example.com> Cc: Sachin Sant <firstname.lastname@example.org>, Michal Hocko <email@example.com>, Linus Torvalds <firstname.lastname@example.org>, LKML <email@example.com>, firstname.lastname@example.org, Mel Gorman <email@example.com>, "Kirill A. Shutemov" <firstname.lastname@example.org>, Andrew Morton <email@example.com>, firstname.lastname@example.org, Christopher Lameter <email@example.com>, Joonsoo Kim <firstname.lastname@example.org>, Kirill Tkhai <email@example.com> Subject: Re: [PATCH 1/3] powerpc/numa: Set numa_node for all possible cpus Date: Fri, 13 Mar 2020 16:52:44 +0530 [thread overview] Message-ID: <20200313112244.GC25144@linux.vnet.ibm.com> (raw) In-Reply-To: <firstname.lastname@example.org> * Vlastimil Babka <email@example.com> [2020-03-12 17:41:58]: > On 3/12/20 5:13 PM, Srikar Dronamraju wrote: > > * Vlastimil Babka <firstname.lastname@example.org> [2020-03-12 14:51:38]: > > > >> > * Vlastimil Babka <email@example.com> [2020-03-12 10:30:50]: > >> > > >> >> On 3/12/20 9:23 AM, Sachin Sant wrote: > >> >> >> On 12-Mar-2020, at 10:57 AM, Srikar Dronamraju <firstname.lastname@example.org> wrote: > >> >> >> * Michal Hocko <email@example.com> [2020-03-11 12:57:35]: > >> >> >>> On Wed 11-03-20 16:32:35, Srikar Dronamraju wrote: > >> I think we do need well defined and documented rules around node_to_mem_node(), > >> cpu_to_node(), existence of NODE_DATA, various node_states bitmaps etc so > >> everyone handles it the same, safe way. > > So let's try to brainstorm how this would look like? What I mean are some rules > like below, even if some details in my current understanding are most likely > incorrect: > Agree. > with nid present in: > N_POSSIBLE - pgdat might not exist, node_to_mem_node() must return some online > node with memory so that we don't require everyone to search for it in slightly > different ways > N_ONLINE - pgdat must exist, there doesn't have to be present memory, > node_to_mem_node() still has to return something else (?) Right, think this has been taken care of at this time. > N_NORMAL_MEMORY - there is present memory, node_to_mem_node() returns itself > N_HIGH_MEMORY - node has present high memory > dont see any problems with the above two to. That leaves us with N_POSSIBLE. > > > > Other option would be to tweak Kirill Tkhai's patch such that we call > > kvmalloc_node()/kzalloc_node() if node is online and call kvmalloc/kvzalloc > > if the node is offline. > > I really would like a solution that hides these ugly details from callers so > they don't have to workaround the APIs we provide. kvmalloc_node() really > shouldn't crash, and it should fallback automatically if we don't give it > __GFP_THISNODE > Agree thats its better to make API's robust where possible. > However, taking a step back, memcg_alloc_shrinker_maps() is probably rather > wasteful on systems with 256 possible nodes and only few present, by allocating > effectively dead structures for each memcg. > If we dont allocate now, we would have to allocate them when we online the nodes. To me it looks better to allocate as soon as the nodes are onlined, > SLUB tries to be smart, so it allocates the per-node per-cache structures only > when the node goes online in slab_mem_going_online_callback(). This is why > there's a crash when such non-existing structures are accessed for a node that's > not online, and why they shouldn't be accessed. > > Perhaps memcg should do the same on-demand allocation, if possible. > Right. -- Thanks and Regards Srikar Dronamraju
next prev parent reply other threads:[~2020-03-13 11:27 UTC|newest] Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-03-11 11:02 [PATCH 0/3] Offline memoryless cpuless node 0 Srikar Dronamraju 2020-03-11 11:02 ` [PATCH 1/3] powerpc/numa: Set numa_node for all possible cpus Srikar Dronamraju 2020-03-11 11:57 ` Michal Hocko 2020-03-12 5:27 ` Srikar Dronamraju 2020-03-12 8:23 ` Sachin Sant 2020-03-12 9:30 ` Vlastimil Babka 2020-03-12 13:14 ` Srikar Dronamraju 2020-03-12 13:51 ` Vlastimil Babka 2020-03-12 16:13 ` Srikar Dronamraju 2020-03-12 16:41 ` Vlastimil Babka 2020-03-13 9:47 ` Joonsoo Kim 2020-03-13 11:04 ` Srikar Dronamraju 2020-03-13 11:38 ` Vlastimil Babka 2020-03-16 8:15 ` Joonsoo Kim 2020-03-13 11:22 ` Srikar Dronamraju [this message] 2020-03-16 9:06 ` Michal Hocko 2020-03-17 13:44 ` Vlastimil Babka 2020-03-17 14:01 ` Michal Hocko 2020-03-11 11:02 ` [PATCH 2/3] powerpc/numa: Prefer node id queried from vphn Srikar Dronamraju 2020-03-11 11:02 ` [PATCH 3/3] mm/page_alloc: Keep memoryless cpuless node 0 offline Srikar Dronamraju 2020-03-15 14:20 ` Christopher Lameter 2020-03-16 8:54 ` Michal Hocko 2020-03-18 7:50 ` Srikar Dronamraju 2020-03-18 18:57 ` Christopher Lameter
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