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[2003:cb:c71c:4e00:b097:7075:f6ba:300a]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-36d2716e3b3sm4407425f8f.42.2024.08.09.00.31.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 09 Aug 2024 00:31:08 -0700 (PDT) Message-ID: Date: Fri, 9 Aug 2024 09:31:06 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 3/3] mm: don't account memmap per-node To: Pasha Tatashin , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-cxl@vger.kernel.org, cerasuolodomenico@gmail.com, hannes@cmpxchg.org, j.granados@samsung.com, lizhijian@fujitsu.com, muchun.song@linux.dev, nphamcs@gmail.com, rientjes@google.com, rppt@kernel.org, souravpanda@google.com, vbabka@suse.cz, willy@infradead.org, dan.j.williams@intel.com, yi.zhang@redhat.com, alison.schofield@intel.com, yosryahmed@google.com References: <20240808213437.682006-1-pasha.tatashin@soleen.com> <20240808213437.682006-4-pasha.tatashin@soleen.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: B0D5A140011 X-Stat-Signature: fi75piaiiw87hdhn4bxqd6sjsauzbxnr X-Rspam-User: X-HE-Tag: 1723188672-455445 X-HE-Meta: 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 gefX6pfM 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 08.08.24 23:34, Pasha Tatashin wrote: > Fix invalid access to pgdat during hot-remove operation: > ndctl users reported a GPF when trying to destroy a namespace: > $ ndctl destroy-namespace all -r all -f > Segmentation fault > dmesg: > Oops: general protection fault, probably for > non-canonical address 0xdffffc0000005650: 0000 [#1] PREEMPT SMP KASAN > PTI > KASAN: probably user-memory-access in range > [0x000000000002b280-0x000000000002b287] > CPU: 26 UID: 0 PID: 1868 Comm: ndctl Not tainted 6.11.0-rc1 #1 > Hardware name: Dell Inc. PowerEdge R640/08HT8T, BIOS > 2.20.1 09/13/2023 > RIP: 0010:mod_node_page_state+0x2a/0x110 > > cxl-test users report a GPF when trying to unload the test module: > $ modrpobe -r cxl-test > dmesg > BUG: unable to handle page fault for address: 0000000000004200 > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > PGD 0 P4D 0 > Oops: Oops: 0000 [#1] PREEMPT SMP PTI > CPU: 0 UID: 0 PID: 1076 Comm: modprobe Tainted: G O N 6.11.0-rc1 #197 > Tainted: [O]=OOT_MODULE, [N]=TEST > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/15 > RIP: 0010:mod_node_page_state+0x6/0x90 > > Currently, when memory is hot-plugged or hot-removed the accounting is > done based on the assumption that memmap is allocated from the same node > as the hot-plugged/hot-removed memory, which is not always the case. > > In addition, there are challenges with keeping the node id of the memory > that is being remove to the time when memmap accounting is actually > performed: since this is done after remove_pfn_range_from_zone(), and > also after remove_memory_block_devices(). Meaning that we cannot use > pgdat nor walking though memblocks to get the nid. > > Given all of that, account the memmap overhead system wide instead. > > For this we are going to be using global atomic counters, but given that > memmap size is rarely modified, and normally is only modified either > during early boot when there is only one CPU, or under a hotplug global > mutex lock, therefore there is no need for per-cpu optimizations. > > Also, while we are here rename nr_memmap to nr_memmap_pages, and > nr_memmap_boot to nr_memmap_boot_pages to be self explanatory that the > units are in page count. > > Reported-by: Yi Zhang > Closes: https://lore.kernel.org/linux-cxl/CAHj4cs9Ax1=CoJkgBGP_+sNu6-6=6v=_L-ZBZY0bVLD3wUWZQg@mail.gmail.com > Reported-by: Alison Schofield > Closes: https://lore.kernel.org/linux-mm/Zq0tPd2h6alFz8XF@aschofie-mobl2/#t > > Fixes: 15995a352474 ("mm: report per-page metadata information") > Signed-off-by: Pasha Tatashin > Tested-by: Dan Williams > --- [...] In general Acked-by: David Hildenbrand Two nits below: > static void free_map_bootmem(struct page *memmap) > diff --git a/mm/vmstat.c b/mm/vmstat.c > index 6f8aa4766f16..ad82c1bf0e63 100644 > --- a/mm/vmstat.c > +++ b/mm/vmstat.c > @@ -1033,6 +1033,23 @@ unsigned long node_page_state(struct pglist_data *pgdat, > } > #endif > > +/* > + * Count number of pages "struct page" and "struct page_ext" consume. > + * nr_memmap_boot: # of pages allocated by boot allocator & not part of MemTotal > + * nr_memmap: # of pages that were allocated by buddy allocator > + */ > +static atomic_long_t nr_memmap_boot, nr_memmap; I *think* the clean and portable way to do it is use ATOMIC_INIT(0) for both. [even though what you have likely works on all archs] > + > +void mod_memmap_boot(long delta) > +{ > + atomic_long_add(delta, &nr_memmap_boot); > +} > + > +void mod_memmap(long delta) > +{ > + atomic_long_add(delta, &nr_memmap); > +} > + Nit picking: (up to you) I'd do it similar to totalram_pages_add(): memmap_pages_add() memmap_boot_pages_add() And call the variables something like static atomic_long_t memmap_pages_boot, memmap_pages; -- Cheers, David / dhildenb