Go Memory Increase

原文链接

Runtime Go 1.12 significantly improves the performance of sweeping when a large fraction of the heap remains live. This reduces allocation latency immediately following a garbage collection.

(中间省略 2 段不太相关的内容) On Linux, the runtime now uses MADV_FREE to release unused memory. This is more efficient but may result in higher reported RSS. The kernel will reclaim the unused data when it is needed.

#include <stdio.h>
#include <string.h>
#include <unistd.h>

int main() {
    char *p = NULL;
    const int MB = 1024 * 1024;
    while (1) {
        p = malloc(100 * MB);
        memset(p, 0, 100 * MB);
        sleep(1);
    }
    return 0;
}

3261164 xxx     20   0 52.375g 0.035t  36524 S 579.1 66.0  16711:10 [打码]       
2321665 xxx     20   0 16.358g 0.016t 569088 S  38.4  1.5   1128:45 ./test  

1. Go 1.12 升级能降低内存分配的延迟，但会导致进程 RSS 变高
2. 因为 Go 1.12 用 MADV_FREE，会让内核延迟回收内存
3. 通过在页表中做标记的方式，延迟内存的分配和回收，可以提高内存管理的效率
4. 可以通过气球来让 OS/Hypervisor 挤占内存，另作他用