tree: https://github.com/alibaba/cloud-kernel.git linux-next head: 1d6103ae4cce545c231de9498d0e70564e7b734e commit: 279df2ffcc1de5b6f8c584b23998f426257ae983 [10894/11168] alinux: doc: Add Documentation/alibaba/interfaces.rst reproduce: make htmldocs If you fix the issue, kindly add following tag as appropriate Reported-by: kbuild test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>, old ones prefixed by <<): reST markup error: vim +97 Documentation/alibaba/interfaces.rst 8 9 memory.wmark_min_adj 10 ==================== 11 This file is under memory cgroup v1. 12 13 In co-location environment, there are more or less some memory 14 overcommitment, then BATCH tasks may break the shared global min 15 watermark resulting in all types of applications falling into 16 the direct reclaim slow path hurting the RT of LS tasks. 17 (NOTE: BATCH tasks tolerate big latency spike even in seconds 18 as long as doesn't hurt its overal throughput. While LS tasks 19 are very Latency-Sensitive, they may time out or fail in case 20 of sudden latency spike lasts like hundreds of ms typically.) 21 22 Actually BATCH tasks are not sensitive to memory latency, they 23 can be assigned a strict min watermark which is different from 24 that of LS tasks(which can be aissgned a lenient min watermark 25 accordingly), thus isolating each other in case of global memory 26 allocation. 27 28 memory.wmark_min_adj stands for memcg global WMARK_MIN adjustment, 29 it is used to realize separate min watermarks above-mentioned for 30 memcgs, its valid value is within [-25, 50], specifically: 31 negative value means to be relative to [0, WMARK_MIN], 32 positive value means to be relative to [WMARK_MIN, WMARK_LOW]. 33 34 For examples:: 35 36 -25 means memcg WMARK_MIN is "WMARK_MIN + (WMARK_MIN - 0) * (-25%)" 37 50 means memcg WMARK_MIN is "WMARK_MIN + (WMARK_LOW - WMARK_MIN) * 50%" 38 39 Negative memory.wmark_min_adj means high QoS requirements, it can 40 allocate below the global WMARK_MIN, which is kind of like the idea 41 behind ALLOC_HARDER, see gfp_to_alloc_flags(). 42 43 Positive memory.wmark_min_adj means low QoS requirements, thus when 44 allocation broke memcg min watermark, it should trigger direct reclaim 45 traditionally, and we trigger throttle instead to further prevent them 46 from disturbing others. The throttle time is simply linearly proportional 47 to the pages consumed below memcg's min watermark. The normal throttle 48 time once should be within [1ms, 100ms], and the maximal throttle time 49 is 1000ms. The throttle is only triggered under global memory pressure. 50 51 With this interface, we can assign positive values for BATCH memcgs 52 and negative values for LS memcgs. Note that root memcg doesn't have 53 this file. 54 55 memory.wmark_min_adj default value is 0, and inherit from its parent, 56 Note that the final effective wmark_min_adj will consider all the 57 hierarchical values, its value is the maximal(most conservative) 58 wmark_min_adj along the hierarchy but excluding intermediate default 59 values(zero). 60 61 For example:: 62 63 The following hierarchy 64 root 65 / \ 66 A D 67 / \ 68 B C 69 / \ 70 E F 71 72 wmark_min_adj: A -10, B -25, C 0, D 50, E -25, F 50 73 wmark_min_eadj: A -10, B -10, C 0, D 50, E -10, F 50 74 75 "echo xxx > memory.wmark_min_adj" set "wmark_min_adj". 76 "cat memory.wmark_min_adj" shows the value of "wmark_min_eadj". 77 78 memory.exstat 79 ============= 80 This file is under memory cgroup v1. 81 82 memory.exstat stands for "extra/extended memory.stat", which is supposed 83 to provide hierarchical statistics. 84 85 "wmark_min_throttled_ms" field is the total throttled time in milliseconds 86 due to positive memory.wmark_min_adj under global memory pressure. 87 88 zombie memcgs reaper 89 ==================== 90 After memcg was deleted, page caches still reference to this memcg 91 causing large number of dead(zombie) memcgs in the system. Then it 92 slows down access to "/sys/fs/cgroup/cpu/memory.stat", etc due to 93 tons of iterations, further causing various latencies. "zombie memcgs 94 reaper" is a tool to reclaim these dead memcgs. It has two modes: 95 96 "Background kthread reaper" mode --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org