mem

• mem
  • mem-regions
    • stack
    • heap
  • jvm
    • gc
  • v8
    • gc
    • mem-leak
    • callback and promise in mem
  • go-vm
    • memory-allocation
    • gc
  • rust-mem

mem-regions

• deepu.tech/memory-mana…
• docs.oracle.com/en/java/jav… 牛逼，必须读

stack

• stack frames
• stack overflow errors

heap

• look up the data in heap using pointers
• out of memory errors
• Manual memory management VS GC(js,go,java)

jvm

• docs.oracle.com/en/java/jav…

• stack

  • thread stack: -Xss
  • local stack

• heap

  • YG: eden + s0 + s1, YGC(minor gc: eden 空间不足)
  • OG: OGC(major gc)
  • GC:

• mem native

  • mataspace:(old PG),class definitions,static,final
  • direct memory

jvm params

-Xms(heap Initial)
-Xmx(heap Max)
-Xss(Thread stack initial)
-XX:MetaspaceSize
-XX:MaxMetaspaceSize
-XX:+UseSerialGC | +UseParallelGC | +UseG1GC | +UseZGC => 自己选

gc

使用daemon thread(分析可用的场景)

• gc 使用的算法
  • marking(标记): GC roots(Stack pointers)
  • Sweeping(清除):
  • Compacting(压缩):
• GC 算法选择标准
  • Throughput：执行gc时间, =>吞吐量=application/(gc + application)
  • Pause-time：STW(stop-the-world,主要发生在marking阶段)时间， => 适合web应用
  • Footprint：Size of the heap used
• gc collector 回收器
  • -XX:+UseSerialGC
  • -XX:+UseParallelGC
  • -XX:+UseG1GC: low pause times and high throughput
  • -XX:+UseZGC: low latency, no stw
• gc 过程
  • minor gc: eden 空间不足出发YGC
  • major gc
    • System.gc(), Runtime.getRunTime().gc()
    • OG 空间不足
    • mataspace 空间不足
    • YGC不管用，minor gc 执行完空间依然不足

v8

• v8.dev/blog/trash-…

又叫 Resident Set

• V8 is written in C++ and can be embedded in any C++ application(兼容C++)
• JavaScript is single-threaded V8 also uses a single process per JavaScript context(单进程，单线程)
• if you use service workers it will spawn a new V8 process per worker.(不是多线程)
• en.wikipedia.org/wiki/Mmap mmap

gc

• stack

• heap

  • New Space:(YG = s0 + s1),Minor GC
  • Old Space:(OG),Major GC(Mark-Sweep & Mark-Compact)
    • Old pointer space：object里面有pointer
    • Old data space: object里面只有数据
  • Large object space:
  • Code-space:
  • Cell space, property cell space, and map space:
    • Cells, PropertyCells,Maps => Map经常用

• class, funcction 定义都在heap里面，类似PG，新生成的对象使用YG + OG(使用stack pointer(gc-root)管理)

• Global stack frame => 全局栈，OS管理, 不会OOM，但heap会发生OOM

# New Space = two semi-space, using Scavenger(Minor GC)
--min_semi_space_size(Initial)
--max_semi_space_size(Max)
# Old Space: using Major GC(Mark-Sweep & Mark-Compact)
--initial_old_space_size(Initial)
--max_old_space_size(Max)
# stack
 --stack_size

• tagged pointers 标记指针
• Minor GC (Scavenger) => YG,
• Major GC(Mark-Sweep-Compact)=> OG
  • marking: gc-root + DFS(深度loop)

mem-leak

callback and promise in mem

• felixgerschau.com/javascript-…
• felixgerschau.com/javascript-…
• deepu.tech/memory-mana…
• felixgerschau.com/javascript-…

go-vm

• https://www.ardanlabs.com/blog/2018/08/scheduling-in-go-part2.html
• P/M/G （Go scheduler机制）
  • logical processor ： 逻辑cpu
• Resident Set
  • stack( =>G，每个goroutine)
  • mheap(page in 8K-32K， =>P,对应processor)
    • arena(mcentral):64M
    • mcache(mspan: span/nospan)
• escape analysis 逃逸分析

memory-allocation

gc

rust-mem