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Mon, 28 Jul 2025 08:15:53 +0000 Date: Mon, 28 Jul 2025 10:15:47 +0200 From: Oscar Salvador To: david@redhat.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Michal Hocko , Hannes Reinecke Subject: [RFC] Disable auto_movable_ratio for selfhosted memmap Message-ID: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Spam-Level: X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.999]; MIME_GOOD(-0.10)[text/plain]; ARC_NA(0.00)[]; MISSING_XM_UA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; RCPT_COUNT_FIVE(0.00)[5] X-Spam-Flag: NO X-Spam-Score: -4.30 Hi, Currently, we have several mechanisms to pick a zone for the new memory we are onlining. Eventually, we will land on zone_for_pfn_range() which will pick the zone. Two of these mechanisms are 'movable_node' and 'auto-movable' policy. The former will put every single hotpluggled memory in ZONE_MOVABLE (unless we can keep zones contiguous by not doing so), while the latter will put it in ZONA_MOVABLE IFF we are within the established ratio MOVABLE:KERNEL. It seems, the later doesn't play well with CXL memory where CXL cards hold really large amounts of memory, making the ratio fail, and since CXL cards must be removed as a unit, it can't be done if any memory block fell within !ZONE_MOVABLE zone. One way to tackle this would be update the ratio every time a new CXL card gets inserted, but this seems suboptimal. Another way is that since CXL memory works with selfhosted memmap, we could relax the check when 'auto-movable' and only look at the ratio if we aren't working with selfhosted memmap. Something like the following (acthung: it's just a PoC) Comments? Ideas? diff --git a/drivers/base/memory.c b/drivers/base/memory.c index 5c6c1d6bb59f..ff87cfb3881a 100644 --- a/drivers/base/memory.c +++ b/drivers/base/memory.c @@ -234,7 +234,7 @@ static int memory_block_online(struct memory_block *mem) return -EHWPOISON; zone = zone_for_pfn_range(mem->online_type, mem->nid, mem->group, - start_pfn, nr_pages); + start_pfn, nr_pages, mem->altmap); /* * Although vmemmap pages have a different lifecycle than the pages @@ -473,11 +473,11 @@ static ssize_t phys_device_show(struct device *dev, static int print_allowed_zone(char *buf, int len, int nid, struct memory_group *group, unsigned long start_pfn, unsigned long nr_pages, - int online_type, struct zone *default_zone) + int online_type, struct zone *default_zone, struct vmem_altmap *altmap) { struct zone *zone; - zone = zone_for_pfn_range(online_type, nid, group, start_pfn, nr_pages); + zone = zone_for_pfn_range(online_type, nid, group, start_pfn, nr_pages, altmap); if (zone == default_zone) return 0; @@ -509,13 +509,13 @@ static ssize_t valid_zones_show(struct device *dev, } default_zone = zone_for_pfn_range(MMOP_ONLINE, nid, group, - start_pfn, nr_pages); + start_pfn, nr_pages, mem->altmap); len = sysfs_emit(buf, "%s", default_zone->name); len += print_allowed_zone(buf, len, nid, group, start_pfn, nr_pages, - MMOP_ONLINE_KERNEL, default_zone); + MMOP_ONLINE_KERNEL, default_zone, mem->altmap); len += print_allowed_zone(buf, len, nid, group, start_pfn, nr_pages, - MMOP_ONLINE_MOVABLE, default_zone); + MMOP_ONLINE_MOVABLE, default_zone, mem->altmap); len += sysfs_emit_at(buf, len, "\n"); return len; } diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h index 23f038a16231..89f7b9c5d995 100644 --- a/include/linux/memory_hotplug.h +++ b/include/linux/memory_hotplug.h @@ -328,7 +328,7 @@ extern struct page *sparse_decode_mem_map(unsigned long coded_mem_map, unsigned long pnum); extern struct zone *zone_for_pfn_range(int online_type, int nid, struct memory_group *group, unsigned long start_pfn, - unsigned long nr_pages); + unsigned long nr_pages, struct vmem_altmap *altmap); extern int arch_create_linear_mapping(int nid, u64 start, u64 size, struct mhp_params *params); void arch_remove_linear_mapping(u64 start, u64 size); diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 69a636e20f7b..6c6600a9c839 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1048,7 +1048,7 @@ static inline struct zone *default_zone_for_pfn(int nid, unsigned long start_pfn struct zone *zone_for_pfn_range(int online_type, int nid, struct memory_group *group, unsigned long start_pfn, - unsigned long nr_pages) + unsigned long nr_pages, struct vmem_altmap *altmap) { if (online_type == MMOP_ONLINE_KERNEL) return default_kernel_zone_for_pfn(nid, start_pfn, nr_pages); @@ -1056,6 +1056,10 @@ struct zone *zone_for_pfn_range(int online_type, int nid, if (online_type == MMOP_ONLINE_MOVABLE) return &NODE_DATA(nid)->node_zones[ZONE_MOVABLE]; + /* Selfhosted memmap, skip ratio check */ + if (online_policy == ONLINE_POLICY_AUTO_MOVABLE && altmap) + return &NODE_DATA(nid)->node_zones[ZONE_MOVABLE]; + if (online_policy == ONLINE_POLICY_AUTO_MOVABLE) return auto_movable_zone_for_pfn(nid, group, start_pfn, nr_pages); -- Oscar Salvador SUSE Labs