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