linux/mm/memory_hotplug.c, branch v4.0

mm/memory hotplug: postpone the reset of obsolete pgdat

2015-03-25T23:20:30Z

Qiu Xishi reported the following BUG when testing hot-add/hot-remove node under stress condition: BUG: unable to handle kernel paging request at 0000000000025f60 IP: next_online_pgdat+0x1/0x50 PGD 0 Oops: 0000 [#1] SMP ACPI: Device does not support D3cold Modules linked in: fuse nls_iso8859_1 nls_cp437 vfat fat loop dm_mod coretemp mperf crc32c_intel ghash_clmulni_intel aesni_intel ablk_helper cryptd lrw gf128mul glue_helper aes_x86_64 pcspkr microcode igb dca i2c_algo_bit ipv6 megaraid_sas iTCO_wdt i2c_i801 i2c_core iTCO_vendor_support tg3 sg hwmon ptp lpc_ich pps_core mfd_core acpi_pad rtc_cmos button ext3 jbd mbcache sd_mod crc_t10dif scsi_dh_alua scsi_dh_rdac scsi_dh_hp_sw scsi_dh_emc scsi_dh ahci libahci libata scsi_mod [last unloaded: rasf] CPU: 23 PID: 238 Comm: kworker/23:1 Tainted: G O 3.10.15-5885-euler0302 #1 Hardware name: HUAWEI TECHNOLOGIES CO.,LTD. Huawei N1/Huawei N1, BIOS V100R001 03/02/2015 Workqueue: events vmstat_update task: ffffa800d32c0000 ti: ffffa800d32ae000 task.ti: ffffa800d32ae000 RIP: 0010: next_online_pgdat+0x1/0x50 RSP: 0018:ffffa800d32afce8 EFLAGS: 00010286 RAX: 0000000000001440 RBX: ffffffff81da53b8 RCX: 0000000000000082 RDX: 0000000000000000 RSI: 0000000000000082 RDI: 0000000000000000 RBP: ffffa800d32afd28 R08: ffffffff81c93bfc R09: ffffffff81cbdc96 R10: 00000000000040ec R11: 00000000000000a0 R12: ffffa800fffb3440 R13: ffffa800d32afd38 R14: 0000000000000017 R15: ffffa800e6616800 FS: 0000000000000000(0000) GS:ffffa800e6600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000025f60 CR3: 0000000001a0b000 CR4: 00000000001407e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: refresh_cpu_vm_stats+0xd0/0x140 vmstat_update+0x11/0x50 process_one_work+0x194/0x3d0 worker_thread+0x12b/0x410 kthread+0xc6/0xd0 ret_from_fork+0x7c/0xb0 The cause is the "memset(pgdat, 0, sizeof(*pgdat))" at the end of try_offline_node, which will reset all the content of pgdat to 0, as the pgdat is accessed lock-free, so that the users still using the pgdat will panic, such as the vmstat_update routine. process A: offline node XX: vmstat_updat() refresh_cpu_vm_stats() for_each_populated_zone() find online node XX cond_resched() offline cpu and memory, then try_offline_node() node_set_offline(nid), and memset(pgdat, 0, sizeof(*pgdat)) zone = next_zone(zone) pg_data_t *pgdat = zone->zone_pgdat; // here pgdat is NULL now next_online_pgdat(pgdat) next_online_node(pgdat->node_id); // NULL pointer access So the solution here is postponing the reset of obsolete pgdat from try_offline_node() to hotadd_new_pgdat(), and just resetting pgdat->nr_zones and pgdat->classzone_idx to be 0 rather than the memset 0 to avoid breaking pointer information in pgdat. Signed-off-by: Gu Zheng Reported-by: Xishi Qiu Suggested-by: KAMEZAWA Hiroyuki Cc: David Rientjes Cc: Yasuaki Ishimatsu Cc: Taku Izumi Cc: Tang Chen Cc: Xie XiuQi Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, memory_hotplug/failure: drain single zone pcplists

2014-12-11T01:41:05Z

Memory hotplug and failure mechanisms have several places where pcplists are drained so that pages are returned to the buddy allocator and can be e.g. prepared for offlining. This is always done in the context of a single zone, we can reduce the pcplists drain to the single zone, which is now possible. The change should make memory offlining due to hotremove or failure faster and not disturbing unrelated pcplists anymore. Signed-off-by: Vlastimil Babka Cc: Naoya Horiguchi Cc: Mel Gorman Cc: Rik van Riel Cc: Yasuaki Ishimatsu Cc: Zhang Yanfei Cc: Xishi Qiu Cc: Vladimir Davydov Cc: Joonsoo Kim Cc: Michal Nazarewicz Cc: Marek Szyprowski Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: introduce single zone pcplists drain

2014-12-11T01:41:05Z

The functions for draining per-cpu pages back to buddy allocators currently always operate on all zones. There are however several cases where the drain is only needed in the context of a single zone, and spilling other pcplists is a waste of time both due to the extra spilling and later refilling. This patch introduces new zone pointer parameter to drain_all_pages() and changes the dummy parameter of drain_local_pages() to be also a zone pointer. When NULL is passed, the functions operate on all zones as usual. Passing a specific zone pointer reduces the work to the single zone. All callers are updated to pass the NULL pointer in this patch. Conversion to single zone (where appropriate) is done in further patches. Signed-off-by: Vlastimil Babka Cc: Naoya Horiguchi Cc: Mel Gorman Cc: Rik van Riel Cc: Yasuaki Ishimatsu Cc: Zhang Yanfei Cc: Xishi Qiu Cc: Vladimir Davydov Cc: Joonsoo Kim Cc: Michal Nazarewicz Cc: Marek Szyprowski Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mem-hotplug: reset node present pages when hot-adding a new pgdat

2014-11-14T00:17:06Z

When memory is hot-added, all the memory is in offline state. So clear all zones' present_pages because they will be updated in online_pages() and offline_pages(). Otherwise, /proc/zoneinfo will corrupt: When the memory of node2 is offline: # cat /proc/zoneinfo ...... Node 2, zone Movable ...... spanned 8388608 present 8388608 managed 0 When we online memory on node2: # cat /proc/zoneinfo ...... Node 2, zone Movable ...... spanned 8388608 present 16777216 managed 8388608 Signed-off-by: Tang Chen Reviewed-by: Yasuaki Ishimatsu Cc: [3.16+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mem-hotplug: reset node managed pages when hot-adding a new pgdat

2014-11-14T00:17:06Z

In free_area_init_core(), zone->managed_pages is set to an approximate value for lowmem, and will be adjusted when the bootmem allocator frees pages into the buddy system. But free_area_init_core() is also called by hotadd_new_pgdat() when hot-adding memory. As a result, zone->managed_pages of the newly added node's pgdat is set to an approximate value in the very beginning. Even if the memory on that node has node been onlined, /sys/device/system/node/nodeXXX/meminfo has wrong value: hot-add node2 (memory not onlined) cat /sys/device/system/node/node2/meminfo Node 2 MemTotal: 33554432 kB Node 2 MemFree: 0 kB Node 2 MemUsed: 33554432 kB Node 2 Active: 0 kB This patch fixes this problem by reset node managed pages to 0 after hot-adding a new node. 1. Move reset_managed_pages_done from reset_node_managed_pages() to reset_all_zones_managed_pages() 2. Make reset_node_managed_pages() non-static 3. Call reset_node_managed_pages() in hotadd_new_pgdat() after pgdat is initialized Signed-off-by: Tang Chen Signed-off-by: Yasuaki Ishimatsu Cc: [3.16+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

memory-hotplug: clear pgdat which is allocated by bootmem in try_offline_node()

2014-10-29T23:33:14Z

When hot adding the same memory after hot removal, the following messages are shown: WARNING: CPU: 20 PID: 6 at mm/page_alloc.c:4968 free_area_init_node+0x3fe/0x426() ... Call Trace: dump_stack+0x46/0x58 warn_slowpath_common+0x81/0xa0 warn_slowpath_null+0x1a/0x20 free_area_init_node+0x3fe/0x426 hotadd_new_pgdat+0x90/0x110 add_memory+0xd4/0x200 acpi_memory_device_add+0x1aa/0x289 acpi_bus_attach+0xfd/0x204 acpi_bus_attach+0x178/0x204 acpi_bus_scan+0x6a/0x90 acpi_device_hotplug+0xe8/0x418 acpi_hotplug_work_fn+0x1f/0x2b process_one_work+0x14e/0x3f0 worker_thread+0x11b/0x510 kthread+0xe1/0x100 ret_from_fork+0x7c/0xb0 The detaled explanation is as follows: When hot removing memory, pgdat is set to 0 in try_offline_node(). But if the pgdat is allocated by bootmem allocator, the clearing step is skipped. And when hot adding the same memory, the uninitialized pgdat is reused. But free_area_init_node() checks wether pgdat is set to zero. As a result, free_area_init_node() hits WARN_ON(). This patch clears pgdat which is allocated by bootmem allocator in try_offline_node(). Signed-off-by: Yasuaki Ishimatsu Cc: Zhang Zhen Cc: Wang Nan Cc: Tang Chen Reviewed-by: Toshi Kani Cc: Dave Hansen Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

memory-hotplug: add sysfs valid_zones attribute

2014-10-10T02:25:52Z

Currently memory-hotplug has two limits: 1. If the memory block is in ZONE_NORMAL, you can change it to ZONE_MOVABLE, but this memory block must be adjacent to ZONE_MOVABLE. 2. If the memory block is in ZONE_MOVABLE, you can change it to ZONE_NORMAL, but this memory block must be adjacent to ZONE_NORMAL. With this patch, we can easy to know a memory block can be onlined to which zone, and don't need to know the above two limits. Updated the related Documentation. [akpm@linux-foundation.org: use conventional comment layout] [akpm@linux-foundation.org: fix build with CONFIG_MEMORY_HOTREMOVE=n] [akpm@linux-foundation.org: remove unused local zone_prev] Signed-off-by: Zhang Zhen Cc: Dave Hansen Cc: David Rientjes Cc: Toshi Kani Cc: Yasuaki Ishimatsu Cc: Naoya Horiguchi Cc: Wang Nan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

memory-hotplug: add zone_for_memory() for selecting zone for new memory

2014-08-07T01:01:21Z

This series of patches fixes a problem when adding memory in bad manner. For example: for a x86_64 machine booted with "mem=400M" and with 2GiB memory installed, following commands cause problem: # echo 0x40000000 > /sys/devices/system/memory/probe [ 28.613895] init_memory_mapping: [mem 0x40000000-0x47ffffff] # echo 0x48000000 > /sys/devices/system/memory/probe [ 28.693675] init_memory_mapping: [mem 0x48000000-0x4fffffff] # echo online_movable > /sys/devices/system/memory/memory9/state # echo 0x50000000 > /sys/devices/system/memory/probe [ 29.084090] init_memory_mapping: [mem 0x50000000-0x57ffffff] # echo 0x58000000 > /sys/devices/system/memory/probe [ 29.151880] init_memory_mapping: [mem 0x58000000-0x5fffffff] # echo online_movable > /sys/devices/system/memory/memory11/state # echo online> /sys/devices/system/memory/memory8/state # echo online> /sys/devices/system/memory/memory10/state # echo offline> /sys/devices/system/memory/memory9/state [ 30.558819] Offlined Pages 32768 # free total used free shared buffers cached Mem: 780588 18014398509432020 830552 0 0 51180 -/+ buffers/cache: 18014398509380840 881732 Swap: 0 0 0 This is because the above commands probe higher memory after online a section with online_movable, which causes ZONE_HIGHMEM (or ZONE_NORMAL for systems without ZONE_HIGHMEM) overlaps ZONE_MOVABLE. After the second online_movable, the problem can be observed from zoneinfo: # cat /proc/zoneinfo ... Node 0, zone Movable pages free 65491 min 250 low 312 high 375 scanned 0 spanned 18446744073709518848 present 65536 managed 65536 ... This series of patches solve the problem by checking ZONE_MOVABLE when choosing zone for new memory. If new memory is inside or higher than ZONE_MOVABLE, makes it go there instead. After applying this series of patches, following are free and zoneinfo result (after offlining memory9): bash-4.2# free total used free shared buffers cached Mem: 780956 80112 700844 0 0 51180 -/+ buffers/cache: 28932 752024 Swap: 0 0 0 bash-4.2# cat /proc/zoneinfo Node 0, zone DMA pages free 3389 min 14 low 17 high 21 scanned 0 spanned 4095 present 3998 managed 3977 nr_free_pages 3389 ... start_pfn: 1 inactive_ratio: 1 Node 0, zone DMA32 pages free 73724 min 341 low 426 high 511 scanned 0 spanned 98304 present 98304 managed 92958 nr_free_pages 73724 ... start_pfn: 4096 inactive_ratio: 1 Node 0, zone Normal pages free 32630 min 120 low 150 high 180 scanned 0 spanned 32768 present 32768 managed 32768 nr_free_pages 32630 ... start_pfn: 262144 inactive_ratio: 1 Node 0, zone Movable pages free 65476 min 241 low 301 high 361 scanned 0 spanned 98304 present 65536 managed 65536 nr_free_pages 65476 ... start_pfn: 294912 inactive_ratio: 1 This patch (of 7): Introduce zone_for_memory() in arch independent code for arch_add_memory() use. Many arch_add_memory() function simply selects ZONE_HIGHMEM or ZONE_NORMAL and add new memory into it. However, with the existance of ZONE_MOVABLE, the selection method should be carefully considered: if new, higher memory is added after ZONE_MOVABLE is setup, the default zone and ZONE_MOVABLE may overlap each other. should_add_memory_movable() checks the status of ZONE_MOVABLE. If it has already contain memory, compare the address of new memory and movable memory. If new memory is higher than movable, it should be added into ZONE_MOVABLE instead of default zone. Signed-off-by: Wang Nan Cc: Zhang Yanfei Cc: Dave Hansen Cc: Ingo Molnar Cc: Yinghai Lu Cc: "Mel Gorman" Cc: Thomas Gleixner Cc: "H. Peter Anvin" Cc: "Luck, Tony" Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Chris Metcalf Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mem-hotplug: introduce MMOP_OFFLINE to replace the hard coding -1

2014-08-07T01:01:16Z

In store_mem_state(), we have: ... 334 else if (!strncmp(buf, "offline", min_t(int, count, 7))) 335 online_type = -1; ... 355 case -1: 356 ret = device_offline(&mem->dev); 357 break; ... Here, "offline" is hard coded as -1. This patch does the following renaming: ONLINE_KEEP -> MMOP_ONLINE_KEEP ONLINE_KERNEL -> MMOP_ONLINE_KERNEL ONLINE_MOVABLE -> MMOP_ONLINE_MOVABLE and introduces MMOP_OFFLINE = -1 to avoid hard coding. Signed-off-by: Tang Chen Cc: Hu Tao Cc: Greg Kroah-Hartman Cc: Lai Jiangshan Cc: Yasuaki Ishimatsu Cc: Gu Zheng Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/memory_hotplug.c: add __meminit to grow_zone_span/grow_pgdat_span

2014-08-07T01:01:15Z

grow_zone_span and grow_pgdat_span are only called by __meminit __add_zone Signed-off-by: Fabian Frederick Cc: Toshi Kani Acked-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds