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2 OpenAnolis cloud-kernel 分析
如果您对Linux的内核系统有一定的了解，并且有需求需要使用Linux内核功能，您可以依据下表提供的Alibaba Cloud Linux 2的内核功能与接口进行相关操作.
| 文档链接 | 说明 |
|---|---|
| 启用cgroup writeback功能 | Alibaba Cloud Linux 2在内核版本4.19.36-12.al7中，对内核接口cgroup v1新增了控制群组回写(cgroup writeback)功能. 该功能使您在使用内核接口cgroup v1时，可以对缓存异步I/O (Buffered I/O) 进行限速. |
| blk-iocost权重限速 | Alibaba Cloud Linux 2在内核版本4.19.81-17.al7.x86_64开始支持基于成本模型(cost model)的权重限速功能，即blk-iocost功能. 该功能是对内核中IO子系统(blkcg)基于权重的磁盘限速功能的进一步完善. |
| 在cgroup v1接口开启PSI功能 | Alibaba Cloud Linux 2在内核版本4.19.81-17.al7中为cgroup v1接口提供了PSI功能. PSI(Pressure Stall Information)是一个可以监控CPU、内存及IO性能异常的内核功能. |
| 修改TCP TIME-WAIT超时时间 | 在Linux的内核中，TCP/IP协议的TIME-WAIT状态持续60秒且无法修改. 但在某些场景下，例如TCP负载过高时，适当调小该值有助于提升网络性能. 因此Alibaba Cloud Linux 2在内核版本4.19.43-13.al7新增内核接口，用于修改TCP TIME-WAIT超时时间. |
| Block IO限流增强监控接口 | 为了更方便地监控Linux block IO限流，Alibaba Cloud Linux 2在内核版本4.19.81-17.al7增加相关接口，用于增强block IO限流的监控统计能力. |
| JBD2优化接口 | JBD2作为ext4文件系统的内核线程，在使用过程中常会遇到影子状态(BH_Shadow)，影响系统性能. 为解决使用JBD2过程中出现的异常，Alibaba Cloud Linux 2在内核版本4.19.81-17.al7对JBD2进行了优化. |
| 跨目录配额创建硬链接 | 默认情况下，ext4文件系统中存在约束，不允许跨目录配额创建硬链接. 但在实际中，某些特定场景有创建硬链接的需求，因此Alibaba Cloud Linux 2提供定制接口，该接口能够绕过ext4文件系统中的约束，实现跨目录配额创建硬链接. |
| 追踪IO时延 | Alibaba Cloud Linux 2优化了IO时延分析工具iostat的原始数据来源/proc/diskstats接口，增加了对设备侧的读、写及特殊IO(discard)等耗时的统计，此外还提供了一个方便追踪IO时延的工具bcc. |
| 检测文件系统和块层的IO hang | IO hang是指在系统运行过程中，因某些IO耗时过长而引起的系统不稳定甚至宕机. 为了准确检测出IO hang，Alibaba Cloud Linux 2扩展核心数据结构，增加了在较小的系统开销下，快速定位并检测IO hang的功能. |
| Memcg全局最低水位线分级 | Alibaba Cloud Linux 2新增了memcg全局最低水位线分级功能. 在global wmark_min的基础上，将资源消耗型任务的global wmark_min上移，使其提前进入直接内存回收. 将时延敏感型业务的global wmark_min下移，使其尽量避免直接内存回收. 这样当资源消耗型任务瞬间申请大量内存的时候，会通过上移的global wmark_min将其短时间抑制，避免时延敏感型业务发生直接内存回收. 等待全局kswapd回收一定量的内存后，再解除资源消耗型任务的短时间抑制. |
| Memcg后台异步回收 | Alibaba Cloud Linux 2增加了memcg粒度的后台异步回收功能. 该功能的实现不同于全局kswapd内核线程的实现，并没有创建对应的memcg kswapd内核线程，而是采用了workqueue机制来实现. |
| cgroup v1接口支持memcg QoS功能 | 内存子系统服务质量(memcg QoS)可以用来控制内存子系统(memcg)的内存使用量的保证(锁定)与限制. Alibaba Cloud Linux 2在4.19.91-18.al7内核版本，新增cgroup v1接口支持memcg QoS的相关功能. |
| Memcg Exstat功能 | Alibaba Cloud Linux 2在4.19.91-18.al7内核版本开始支持的Memcg Exstat(Extend/Extra)功能. |
| TCP-RT功能的配置说明 | Alibaba Cloud Linux 2在内核版本kernel-4.19.91-21.al7开始支持TCP层的服务监控功能(TCP-RT). |
1 SCHED_SLI
git log --oneline | grep alinux | grep -E "sched|cpuacct"
06d7286d7c8e alinux: sched: add kconfig SCHED_SLI
1.1 Latency Histograms
echo 1 > /proc/cpusli/sched_lat_enabled
mount -t tmpfs cgroup_root /sys/fs/cgroup
mkdir -p /sys/fs/cgroup/cpu,cpuacct
mount -t cgroup -o cpu,cpuacct cpu,cpuacct /sys/fs/cgroup/cpu,cpuacct
cpuacct 中引入了一些调度相关的 latency 的统计信息, 并用 histograms 的方式输出.
| 接口 | 描述 | 实现思路 | commit |
|---|---|---|---|
| cpuacct.wait_latency | 在就绪队列里的等待时间 | 统计方式同 wait_sum/wait_start 等计数器. enqueue_entity 入队时开始计时, 出队时结束计时(set_next_entity 准备投入运行时, 也会出队.) | alinux: sched: Introduce cfs scheduling latency histograms |
| cpuacct.cgroup_wait_latency | 在就绪队列里的等待时间 | 统计方式同 wait_sum/wait_start 等计数器. enqueue_entity 入队时开始计时, 出队时结束计时(set_next_entity 准备投入运行时, 也会出队.) | alinux: sched: Add cgroup's scheduling latency histograms |
| cpuacct.block_latency/cpuacct.ioblock_latency | 统计进程 D 状态阻塞的时间(其中 ioblock_latency 统计因为 I/O 阻塞的等待时间) | 更新方式 block_latency 同 block_start, ioblock_latency 同 iowait_sum. 进程出队 update_stats_dequeue 开始计时, 进程入队的时候 update_stats_enqueue_sleeper 停止计时 |
alinux: sched: Add cgroup-level blocked time histograms |
ab81d2d9f745 alinux: sched: Add cpu_stress to show system-wide task waiting
c7462cfec178 alinux: sched: Fix wrong cpuacct_update_latency declaration
fa418988c52e alinux: sched: Finer grain of sched latency
2abfd07b1c1a alinux: sched: Add "nr" to sched latency histogram
6dbaddaa480a alinux: sched: Add cgroup's scheduling latency histograms
a055ee2ce27b alinux: sched: Add cgroup-level blocked time histograms
76d98609f832 alinux: sched: Introduce cfs scheduling latency histograms
1.2 CPUACCT STAT
cpuacct 中引入的 proc_stat 统计了 CGROUP 分组中进程的 CPU 占用/空闲等统计信息
| 接口 | 描述 | 实现思路 | commit |
|---|---|---|---|
| cpuacct.proc_stat | cpuacct 的详细统计信息 | NA | commit 9be0ac2bcbaa ("alinux: cpuacct: export cpuacct.proc_stat interface") |
1c5ab7a7f5d9 alinux: sched: Fix %steal in cpuacct.proc_stat in guest OS
1607a4855848 alinux: sched: Fix regression caused by nr_uninterruptible
1e0cec0b58c7 alinux: sched: make SCHED_SLI dependent on FAIR_GROUP_SCHED
5be663e3cfcf alinux: sched: Fix p->cpu build error on aarch64
435d7069244d alinux: sched: Fix nr_migrations compile errors
9e7b35d6d84e alinux: sched: Introduce per-cgroup iowait accounting
c75529800bf2 alinux: sched: Introduce per-cgroup steal accounting
61e5885959be alinux: sched: Introduce per-cgroup idle accounting
965d75d3785c alinux: cpuacct: make cpuacct record nr_migrations
9410d3142882 alinux: cpuacct: Export nr_running & nr_uninterruptible
004b3ba9ebd3 alinux: sched/cputime: Fix guest cputime of cpuacct.proc_stat
8ab45c97b581 alinux: cpuacct/proc_stat: Consider isolcpus
9be0ac2bcbaa alinux: cpuacct: export cpuacct.proc_stat interface
36da4fe9851a alinux: sched: Maintain "nr_uninterruptible" in runqueue
06d7286d7c8e alinux: sched: add kconfig SCHED_SLI
1.3 PSI V1
1bd8a72b1181 alinux: psi: using cpuacct_cgrp_id under CONFIG_CGROUP_CPUACCT
dc159a61c043 alinux: introduce psi_v1 boot parameter
1f49a7385032 alinux: psi: Support PSI under cgroup v1
MEMSLI
echo 1 > /proc/memsli/enabled
mount -t tmpfs cgroup_root /sys/fs/cgroup
mkdir -p /sys/fs/cgroup/memory
mount -t cgroup -o memory memory /sys/fs/cgroup/memory
2 Scheduler
2.1
bcaf8afd6270 alinux: sched: Add switch for scheduler_tick load tracking
bb48b716f496 alinux: sched: Add switch for update_blocked_averages
d2440c99979d alinux: sched/fair: use static load in wake_affine_weight
2.2 burst 等
db83ac46e3f5 alinux: cpuacct: Export nr_running & nr_uninterruptible
982358c4f1f0 alinux: sched: Maintain "nr_uninterruptible" in runqueue
3a022fb07707 alinux: sched/fair: Fix CPU burst stat
a97cbf90404c alinux: sched/fair: Introduce init buffer into CFS burst
95527c5751fa alinux: sched: Restore upper limit of cfs_b->buffer to max_cfs_runtime
a0b0376bdbdc alinux: sched: Add document for burstable CFS bandwidth control
744d0dc11559 alinux: sched: Add cfs bandwidth burst statistics
739156b53e75 alinux: sched: Make CFS bandwidth controller burstable
d9ba6d0880e3 alinux: sched: Introduce primitives for CFS bandwidth burst
9d168f216486 alinux: sched: Defend cfs and rt bandwidth against overflow
3 MEMORY
49c322d5e62e alinux: mm: Fix the vma merge warning
9eb3033b5452 alinux: meminfo: Add meminfo support for rich container
3bac8a607ab0 alinux: nitro_enclaves: Split mmio region and increase EIF_LOAD_OFFSET
59cec5300f4d alinux: mm: bring back unevictable.o in obj-y
b91b37989d2f alinux: mm: make the swap throttle more accurate
737b01dfdb63 alinux: mm: fix an global-out-of-bounds in __do_proc_doulongvec_minmax
f5ac90f84be8 alinux: mm: add an interface to adjust the penalty time dynamically
f8a6ae902811 alinux: mm: support swap.high for cgroup v1
7ba445112d91 alinux: configs: Enable SM2 asymmetric algorithm
a7e3c096fa8a alinux: tcp_rt module: fix bug of using vfree to release the memory obtained by kmalloc
fc8d2968d054 alinux: arm64: adjust tk_core memory layout
b893a7d56134 alinux: mm: completely disable swapout with negative swappiness
05f6ed402562 alinux: introduce deferred_meminit boot parameter
56a432f556a5 alinux: mm: thp: add fast_cow switch
587136851af8 alinux: mm: fix undefined reference to printk_ratelimit_state
79e7c57a1833 alinux: mm: fix undefined reference to mlock_fixup
a42290726450 alinux: Limit the print message frequency when memcg oom triggers
8962f1257a40 alinux: mm: restrict the print message frequency further when memcg oom triggers
b725e2580207 alinux: Revert "mm/compaction.c: clear total_{migrate,free}_scanned before scanning a new zone"
7d6cb94f148e alinux: mm: Pin code section of process in memory
3d5ca29dd634 alinux: mm, memcg: optimize division operation with memsli counters
055ed63be9b6 alinux: mm, memcg: rework memsli interfaces
9e58d704f63a alinux: mm, memcg: add kconfig MEMSLI
892970b760e2 alinux: mm, memcg: add memsli procfs switch interface
77663a9d54da alinux: mm, memcg: gather memsli/exstat from all possible cpus
6c4e1cc32b45 alinux: mm, memcg: account throttle over memory.high for memcg direct reclaim
ddfd4d5e8f76 alinux: mm, memcg: record latency of swapout and swapin in every memcg
390710798062 alinux: mm, memcg: account reclaim_high for memcg direct reclaim
fe673ccf92aa alinux: mm, memcg: adjust the latency probe point for memcg direct reclaim
837e53abb954 alinux: mm, memcg: rework memory latency histogram interfaces
4bec5cfe97cf alinux: mm, memcg: record latency of direct compact in every memcg
83058e75601e alinux: mm, memcg: record latency of direct reclaim in every memcg
b37fe7db34f4 alinux: mm, memcg: optimize division operation with memcg counters
27393b9b965a alinux: mm, memcg: export workingset counters on memcg v1
ec661706b1c9 alinux: mm, memcg: abort priority oom if with oom victim
2061acd6c236 alinux: mm, memcg: account number of processes in the css
fb4c5ea64934 alinux: mm, memcg: fix soft lockup in priority oom
40969475355a alinux: mm, memcg: record latency of memcg wmark reclaim
```cpp
5028e358bcd4 alinux: mm: oom_kill: show killed task's cgroup info in global oom
7d41295cc97f alinux: mm: memcontrol: enable oom.group on cgroup-v1
0c8648d9554d alinux: doc: alibaba: Add priority oom descriptions
52e375fcb7a7 alinux: mm: memcontrol: introduce memcg priority oom
ef467b9ddbc0 alinux: memcg: Account throttled time due to memory.wmark_min_adj
60be0f545fac alinux: memcg: Introduce memory.wmark_min_adj
63442ea9f838 alinux: memcg: Provide users the ability to reap zombie memcgs
9ea9e641c56a alinux: mm: remove unused variable
25f9e572a7da alinux: mm: kidled: fix frame-larger-than build warning
83cd9d23197d alinux: jbd2: track slow handle which is preventing transaction committing
3e655c51650c alinux: mm,memcg: export memory.{min,low} to cgroup v1
942855175c77 alinux: mm,memcg: export memory.{events,events.local} to v1
7d36553bd29d alinux: mm,memcg: export memory.high to v1
3c40972a47a6 alinux: mm: memcontrol: memcg_wmark_wq can be static
dff2d64b00bc alinux: mm/thp: remove unused variable 'pgdata' in split_huge_page_to_list()
e6ca020bc338 alinux: mm: thp: move deferred split queue to memcg's nodeinfo
a29243e2e890 alinux: mm: Support kidled
bbaee3afa992 alinux: mm: memcontrol: make distance between wmark_low and wmark_high configurable
c69c12cc10ba alinux: mm: vmscan: make memcg kswapd set memcg state to dirty or writeback
6332d4e3580b alinux: mm: memcontrol: treat memcg wmark reclaim work as kswapd
0149d7b9a6ab alinux: mm: memcontrol: add background reclaim support for cgroupv2
6967792f8d41 alinux: mm: memcontrol: support background async page reclaim
49a3b46525f3 alinux: mm: vmscan: make it sane reclaim if cgwb_v1 is enabled
2ced6afdefa9 alinux: mm, memcg: fix possible soft lockup in try_charge
cc00f21eb912 alinux: memcg: Point wb to root memcg/blkcg when offlining to avoid zombie
2307342e80bc alinux: writeback: memcg_blkcg_tree_lock can be static
665e22e9ec59 alinux: writeback: add debug info for memcg-blkcg link
7396367dbfa2 alinux: writeback: add memcg_blkcg_link tree
2e38a0f2950e alinux: mm: add proc interface to control context readahead
10be0b372cac readahead: introduce context readahead algorithm