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[2003:cb:c733:6400:ae10:4bb7:9712:8548]) by smtp.gmail.com with ESMTPSA id i14-20020a05600c354e00b004068de50c64sm11449371wmq.46.2023.10.09.08.04.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 09 Oct 2023 08:04:06 -0700 (PDT) Message-ID: <831b9b12-08fe-f5dc-f21d-83284b0aee8a@redhat.com> Date: Mon, 9 Oct 2023 17:04:05 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH v5 1/2] mm/memory_hotplug: split memmap_on_memory requests across memblocks To: "Huang, Ying" , Vishal Verma Cc: Andrew Morton , Oscar Salvador , Dan Williams , Dave Jiang , linux-kernel@vger.kernel.org, linux-mm@kvack.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, Dave Hansen , "Aneesh Kumar K.V" , Michal Hocko , Jonathan Cameron , Jeff Moyer References: <20231005-vv-kmem_memmap-v5-0-a54d1981f0a3@intel.com> <20231005-vv-kmem_memmap-v5-1-a54d1981f0a3@intel.com> <87jzrylslk.fsf@yhuang6-desk2.ccr.corp.intel.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <87jzrylslk.fsf@yhuang6-desk2.ccr.corp.intel.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: h3nrtryb76ycu9wy54i3ndabnpzjfjtu X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 730FB20030 X-Rspam-User: X-HE-Tag: 1696863852-766257 X-HE-Meta: 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 yoZe9avV OMQvlfB5EMmMLE4RBxJ3MUpjrWNz2Yu1Z/jxFp4lQ0Lu1iFIB9UYENTc0OzFIlemxErFoLjXcMPZ00vk0a/Ces3l/46wQA1ZiLT/qZ1jXbMtmFj/GFkqnG8Amy4oVhEZQVdhed8xAdxPRtIQHydMHul2J9TNZNOrvbTeM5/xpTwX7tFgTq6UvTAhJoCoQAOREgWuQaxwjP4RqPLR1J8WMPgLj75hYY40jr4/WQHX8FHpEIgCRWhZRAnghn8984l3plTKa2tbsu96M8jfzAoaipdQnL84aNXiu0FUIVtYxpHJElAvRCzrZDt/oFnmrzPdI8u351wXfmc5ChsuISQdrCdJbCQMPJk4JBuV86G7a/qR+7csbec6ffkxb+gbf+6/sEK/H1DvlDLTkZJoFDyeYNTgVpAn1ILuxxB3u22mWMJviMy9+TlW6Bo6BltCaj9P9ewl1qEgJY7j2ArkpUXFw5eCrScnxM0NYF6hhnXOx0iUInVhMZviAYuBHkk1ByiWkmdloUG4XVf/gDUfwp868KFhhLNfjLuhTPe3Y6chfCtb+VmF6NOs6MjVfAp8CmGud4miMTc2kVaIzrsHdYfaH0poP/A== 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: On 07.10.23 10:55, Huang, Ying wrote: > Vishal Verma writes: > >> The MHP_MEMMAP_ON_MEMORY flag for hotplugged memory is restricted to >> 'memblock_size' chunks of memory being added. Adding a larger span of >> memory precludes memmap_on_memory semantics. >> >> For users of hotplug such as kmem, large amounts of memory might get >> added from the CXL subsystem. In some cases, this amount may exceed the >> available 'main memory' to store the memmap for the memory being added. >> In this case, it is useful to have a way to place the memmap on the >> memory being added, even if it means splitting the addition into >> memblock-sized chunks. >> >> Change add_memory_resource() to loop over memblock-sized chunks of >> memory if caller requested memmap_on_memory, and if other conditions for >> it are met. Teach try_remove_memory() to also expect that a memory >> range being removed might have been split up into memblock sized chunks, >> and to loop through those as needed. >> >> Cc: Andrew Morton >> Cc: David Hildenbrand >> Cc: Michal Hocko >> Cc: Oscar Salvador >> Cc: Dan Williams >> Cc: Dave Jiang >> Cc: Dave Hansen >> Cc: Huang Ying >> Suggested-by: David Hildenbrand >> Signed-off-by: Vishal Verma >> --- >> mm/memory_hotplug.c | 162 ++++++++++++++++++++++++++++++++-------------------- >> 1 file changed, 99 insertions(+), 63 deletions(-) >> >> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >> index f8d3e7427e32..77ec6f15f943 100644 >> --- a/mm/memory_hotplug.c >> +++ b/mm/memory_hotplug.c >> @@ -1380,6 +1380,44 @@ static bool mhp_supports_memmap_on_memory(unsigned long size) >> return arch_supports_memmap_on_memory(vmemmap_size); >> } >> >> +static int add_memory_create_devices(int nid, struct memory_group *group, >> + u64 start, u64 size, mhp_t mhp_flags) >> +{ >> + struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) }; >> + struct vmem_altmap mhp_altmap = { >> + .base_pfn = PHYS_PFN(start), >> + .end_pfn = PHYS_PFN(start + size - 1), >> + }; >> + int ret; >> + >> + if ((mhp_flags & MHP_MEMMAP_ON_MEMORY)) { >> + mhp_altmap.free = memory_block_memmap_on_memory_pages(); >> + params.altmap = kmalloc(sizeof(struct vmem_altmap), GFP_KERNEL); >> + if (!params.altmap) >> + return -ENOMEM; >> + >> + memcpy(params.altmap, &mhp_altmap, sizeof(mhp_altmap)); >> + } >> + >> + /* call arch's memory hotadd */ >> + ret = arch_add_memory(nid, start, size, ¶ms); >> + if (ret < 0) >> + goto error; >> + >> + /* create memory block devices after memory was added */ >> + ret = create_memory_block_devices(start, size, params.altmap, group); >> + if (ret) >> + goto err_bdev; >> + >> + return 0; >> + >> +err_bdev: >> + arch_remove_memory(start, size, NULL); >> +error: >> + kfree(params.altmap); >> + return ret; >> +} >> + >> /* >> * NOTE: The caller must call lock_device_hotplug() to serialize hotplug >> * and online/offline operations (triggered e.g. by sysfs). >> @@ -1388,14 +1426,10 @@ static bool mhp_supports_memmap_on_memory(unsigned long size) >> */ >> int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) >> { >> - struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) }; >> + unsigned long memblock_size = memory_block_size_bytes(); >> enum memblock_flags memblock_flags = MEMBLOCK_NONE; >> - struct vmem_altmap mhp_altmap = { >> - .base_pfn = PHYS_PFN(res->start), >> - .end_pfn = PHYS_PFN(res->end), >> - }; >> struct memory_group *group = NULL; >> - u64 start, size; >> + u64 start, size, cur_start; >> bool new_node = false; >> int ret; >> >> @@ -1436,28 +1470,21 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) >> /* >> * Self hosted memmap array >> */ >> - if (mhp_flags & MHP_MEMMAP_ON_MEMORY) { >> - if (mhp_supports_memmap_on_memory(size)) { >> - mhp_altmap.free = memory_block_memmap_on_memory_pages(); >> - params.altmap = kmalloc(sizeof(struct vmem_altmap), GFP_KERNEL); >> - if (!params.altmap) >> + if ((mhp_flags & MHP_MEMMAP_ON_MEMORY) && >> + mhp_supports_memmap_on_memory(memblock_size)) { >> + for (cur_start = start; cur_start < start + size; >> + cur_start += memblock_size) { >> + ret = add_memory_create_devices(nid, group, cur_start, >> + memblock_size, >> + mhp_flags); >> + if (ret) >> goto error; >> - >> - memcpy(params.altmap, &mhp_altmap, sizeof(mhp_altmap)); >> } >> - /* fallback to not using altmap */ >> - } >> - >> - /* call arch's memory hotadd */ >> - ret = arch_add_memory(nid, start, size, ¶ms); >> - if (ret < 0) >> - goto error_free; >> - >> - /* create memory block devices after memory was added */ >> - ret = create_memory_block_devices(start, size, params.altmap, group); >> - if (ret) { >> - arch_remove_memory(start, size, NULL); >> - goto error_free; >> + } else { >> + ret = add_memory_create_devices(nid, group, start, size, >> + mhp_flags); >> + if (ret) >> + goto error; >> } >> >> if (new_node) { >> @@ -1494,8 +1521,6 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) >> walk_memory_blocks(start, size, NULL, online_memory_block); >> >> return ret; >> -error_free: >> - kfree(params.altmap); >> error: >> if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) >> memblock_remove(start, size); >> @@ -2146,12 +2171,41 @@ void try_offline_node(int nid) >> } >> EXPORT_SYMBOL(try_offline_node); >> >> -static int __ref try_remove_memory(u64 start, u64 size) >> +static void __ref remove_memory_block_and_altmap(int nid, u64 start, u64 size) >> { >> + int rc = 0; >> struct memory_block *mem; >> - int rc = 0, nid = NUMA_NO_NODE; >> struct vmem_altmap *altmap = NULL; >> >> + rc = walk_memory_blocks(start, size, &mem, test_has_altmap_cb); >> + if (rc) { >> + altmap = mem->altmap; >> + /* >> + * Mark altmap NULL so that we can add a debug >> + * check on memblock free. >> + */ >> + mem->altmap = NULL; >> + } >> + >> + /* >> + * Memory block device removal under the device_hotplug_lock is >> + * a barrier against racing online attempts. >> + */ >> + remove_memory_block_devices(start, size); >> + >> + arch_remove_memory(start, size, altmap); >> + >> + /* Verify that all vmemmap pages have actually been freed. */ >> + if (altmap) { >> + WARN(altmap->alloc, "Altmap not fully unmapped"); >> + kfree(altmap); >> + } >> +} >> + >> +static int __ref try_remove_memory(u64 start, u64 size) >> +{ >> + int rc, nid = NUMA_NO_NODE; >> + >> BUG_ON(check_hotplug_memory_range(start, size)); >> >> /* >> @@ -2167,47 +2221,28 @@ static int __ref try_remove_memory(u64 start, u64 size) >> if (rc) >> return rc; >> >> + mem_hotplug_begin(); >> + >> /* >> - * We only support removing memory added with MHP_MEMMAP_ON_MEMORY in >> - * the same granularity it was added - a single memory block. >> + * For memmap_on_memory, the altmaps could have been added on >> + * a per-memblock basis. Loop through the entire range if so, >> + * and remove each memblock and its altmap. >> */ >> if (mhp_memmap_on_memory()) { > > IIUC, even if mhp_memmap_on_memory() returns true, it's still possible > that the memmap is put in DRAM after [2/2]. So that, > arch_remove_memory() are called for each memory block unnecessarily. Can > we detect this (via altmap?) and call remove_memory_block_and_altmap() > for the whole range? Good point. We should handle memblock-per-memblock onny if we have to handle the altmap. Otherwise, just call a separate function that doesn't care about -- e.g., called remove_memory_blocks_no_altmap(). We could simply walk all memory blocks and make sure either all have an altmap or none has an altmap. If there is a mix, we should bail out with WARN_ON_ONCE(). -- Cheers, David / dhildenb