set_overcommit_ratio.php

set_overcommit_ratio.php

<?php
//sudo crontab -e 里加"* * * * * /usr/bin/php /home/malcolm/set_overcommit_ratio.php"
//MemFree需要保留200MB给系统(否则iowait很高桌面就卡住了), Cached有一部份是释放不掉的, 只能先用drop_caches释放下然后计算剩余内存时就不用算Cached的可释放部分了,
//预算超占率采用130%(firefox新开一个标签页时的超占率130%, chrome新开一个标签页是145%), 这个值是非常保守的, sublime,firefox等程序启动都在190%到220%之间, 也是考虑到每分钟才跑一次预占超出去了后再强行缩小会导致/usr/bin/X挂掉
$start_time=time();
shell_exec('sync && echo 3 > /proc/sys/vm/drop_caches');
$mems=array();
$tmp=explode("\n", trim(shell_exec('cat /proc/meminfo | grep -P "Mem|Commit|Cached"')));
foreach ($tmp as $v)
{
    $v=explode(':', $v);
    $mems[$v[0]]=intval($v[1]);
}
//var_export($mems);
$overcommit_ratio=round(($mems['Committed_AS']+$mems['MemFree']*1.30)/$mems['MemTotal']*100);
//echo $overcommit_ratio."\n";
echo shell_exec("/sbin/sysctl vm.overcommit_memory=2");                     //拒绝分配超过1.3倍， 第一重预防
echo shell_exec("/sbin/sysctl vm.overcommit_ratio={$overcommit_ratio}");
echo shell_exec('pgrep -f "/usr/bin/X" | while read PID; do echo -17 > /proc/$PID/oom_adj; done');    //lxsession内存利用率高不担心, oom统计默认只排除了systemd-udevd和sshd漏了Xorg
while (time()-$start_time<56)    //1分钟还剩不到4秒就不要继续循环了, 避免跟crontab启动的任务重叠
{
    $tmp=explode(':', trim(shell_exec('cat /proc/meminfo | grep -P "MemFree"')), 2);
    $free=intval($tmp[1]);
    $tmp=explode(':', trim(shell_exec('cat /proc/meminfo | grep -P "Buffers"')), 2);
    $buffers=intval($tmp[1]);
    $tmp=explode(':', trim(shell_exec('cat /proc/meminfo | grep -P "Cached"')), 2);
    $cached=intval($tmp[1]);
    $tmp=$free+$buffers+$cached;    //这才是真正剩余的内存
    //echo $tmp."\n";
    if ($tmp>0 && $tmp<200000)    //是numeric并且小于200MB才开始预防性杀oom统计的坏进程, 第二重预防
    {
        $bad=preg_split("/\s+/", trim(@shell_exec('for proc in $(find /proc -maxdepth 1 -regex "/proc/[0-9]+"); do printf "%2d %5d %s\n" "$(cat $proc/oom_score)" "$(basename $proc)" "$(cat $proc/cmdline | tr "\0" " " | head -c 50)"; done 2>/dev/null | sort -nr | head -n 1')), 3);
        //var_export($bad);
        $bad_name=$bad[2];
        $bad=$bad[1];
        echo $bad_name."\n";
        if (is_numeric($bad))
        {
            echo shell_exec("kill -9 {$bad}");
            file_put_contents('/home/malcolm/set_overcommit_ratio.txt', date('Ymd His:').$bad_name."\n", FILE_APPEND);
        }
    }
    sleep(3);
}
?>