一条运维短信引起的思考
刚吃完饭，看到手机来了几条短信，显示内存不够，赶紧登陆机器
发现问题：
8G内存，占用了7G，而我的java进程设置了 -Xms2048m -Xmx2048m ,那内存跑哪去了?
恰好看到azkaban计算可用内存代码，留存一份，代码如下：
private static void readMemoryInfoFile() {
BufferedReader br = null;
try {
br = new BufferedReader(new FileReader(MEMINFO_FILE));
long sizeMemFree = 0;
long sizeBuffers = 0;
long sizeCached = 0;
long sizeSwapCached = 0;
int count = 0;
String line = br.readLine();
while (line != null) {
if (line.startsWith("MemFree:") || line.startsWith("Buffers:")
|| line.startsWith("Cached") || line.startsWith("SwapCached")) {
int idx1 = line.indexOf(":");
int idx2 = line.lastIndexOf("kB");
String strSize = line.substring(idx1+1, idx2-1).trim();
if (line.startsWith("MemFree:")) {
sizeMemFree = Long.parseLong(strSize);
} else if (line.startsWith("Buffers:")) {
sizeBuffers = Long.parseLong(strSize);
} else if (line.startsWith("Cached:")) {
sizeCached = Long.parseLong(strSize);
} else if (line.startsWith("SwapCached:")) {
sizeSwapCached = Long.parseLong(strSize);
}
//all lines read
if (++count == 4) {
break;
}
}
line = br.readLine();
}
if (count < 4) {
logger.error("Error: less than 4 rows read from /proc/meminfo for free memory information");
}
long sizeTotal = sizeMemFree + sizeBuffers + sizeCached + sizeSwapCached;
logger.info(String.format("Current system free memory is %d kb (MemFree %d, Buffers %d, Cached %d, SwapCached %d)",
sizeTotal, sizeMemFree, sizeBuffers, sizeCached, sizeSwapCached));
if (sizeTotal > 0) {
updateFreeMemAmount(sizeTotal);
}
} catch (IOException e) {
logger.error("Exception in reading memory info file", e);
} finally {
try {
if (br != null) {
br.close();
}
} catch (IOException e) {
logger.error("Exception in closing the buffered reader", e);
}
}
}
以后别不知道怎么计算一个机器的可用内存了哈！
命令行的方式就是
cat /proc/meminfo | grep -E "^MemTotal:|^MemFree:|^Buffers:|^Cached:|^SwapCached:"
参考：
azkaban.execapp.ServerStatisticsServlet.fillRemainingMemoryPercent