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<div class="moz-cite-prefix">On 06/18/2016 03:21 PM, ahmet mırçık
wrote:<br>
</div>
<blockquote
cite="mid:CADoNL8OuWoRZbLAOVw6LZgowJfrdGPF1nCzhjSDHUBaGdUANBg@mail.gmail.com"
type="cite">
<div dir="ltr">
<p style="color:rgb(0,0,0);font-size:12.8px">Hi, </p>
<p style="color:rgb(0,0,0);font-size:12.8px">I am running a test
which is trying to log memory info. when free-heap-percentage
is under a certain threshold. But noticed that when heap is
around `-XX:CMSInitiatingOccupancyFraction`,
Runtime.getRuntime().freeMemory() can report wrong values when
compared to memory info from GC logs. It reports as if whole
heap is nearly occupied, but actually there exists lots of
free-memory. Issue is observable for a short-time period.
Later it starts to report expected values. (Also tried my test
with G1 defaults and Runtime.getRuntime().freeMemory()
reported as expected)</p>
</div>
</blockquote>
<br>
From the latest log (with PrintGCDetails) is this an example of the
<br>
freeMemory being wrong but it gets better?<br>
<br>
runtime.maxMemory=61207M, runtime.totalMemory=61207M, <font
color="#ff0000">runtime.freeMemory=319M</font>,
runtime.usedMemory=60887M, runTime.availableMemory=319M,
freeHeapPercentage=0.52<br>
99.641: [CMS-concurrent-reset: 0.122/0.122 secs] [Times: user=0.67
sys=0.01, real=0.12 secs]<br>
99.896: [GC99.896: [ParNew: 2146944K->238528K(2146944K),
0.5846780 secs] 51929136K->51910762K(62676032K), 0.5847860 secs]
[Times: user=5.33 sys=0.92, real=0.58 secs]<br>
100.484: [GC [1 CMS-initial-mark: 51672234K(60529088K)]
51925538K(62676032K), 0.0461750 secs] [Times: user=0.05 sys=0.00,
real=0.05 secs]<br>
100.530: [CMS-concurrent-mark-start]<br>
102.959: [GC102.959: [ParNew: 2146944K->238528K(2146944K),
0.5868320 secs] 53819178K->53798644K(62676032K), 0.5869410 secs]
[Times: user=6.25 sys=0.88, real=0.59 secs] <br>
runtime.maxMemory=61207M,<font color="#ff0000">
runtime.totalMemory=61207M</font>, runtime.freeMemory=7344M,
runtime.usedMemory=53862M, runTime.availableMemory=7344M,
freeHeapPercentage=12.00<br>
<br>
Jon<br>
<br>
<blockquote
cite="mid:CADoNL8OuWoRZbLAOVw6LZgowJfrdGPF1nCzhjSDHUBaGdUANBg@mail.gmail.com"
type="cite">
<div dir="ltr">
<p style="color:rgb(0,0,0);font-size:12.8px">Issue is easily
visible on large heaps.</p>
<p style="color:rgb(0,0,0);font-size:12.8px">Is my assumption
correct? Can Runtime.getRuntime().freeMemory() report wrong
free-memory info for a while? Or how can we explain this
situation?</p>
<p style="color:rgb(0,0,0);font-size:12.8px">Here is my test and
how i run it from command line:</p>
<pre style="white-space:pre-wrap;color:rgb(0,0,0);word-wrap:break-word"><font color="#000000">[PROBLEMATIC RUN WITH CMS]--> java -verbose:gc -Xms60G -Xmx60G -XX:CMSInitiatingOccupancyFraction=2 -XX:+UseConcMarkSweepGC -XX:+UseParNewGC -cp target/free-memory-issue-1.0-SNAPSHOT.jar FreeMemory
</font></pre>
<pre style="white-space:pre-wrap;color:rgb(0,0,0);word-wrap:break-word"><pre style="white-space:pre-wrap;word-wrap:break-word">[OK RUN WITH G1]--> java -verbose:gc -Xms60G -Xmx60G -XX:+UseG1GC -cp target/free-memory-issue-1.0-SNAPSHOT.jar FreeMemory</pre></pre>
<pre style="white-space:pre-wrap;color:rgb(0,0,0);word-wrap:break-word">public class FreeMemory {
static final int MB = 1024 * 1024;
static final String MESSAGE = "runtime.maxMemory=%d%s, runtime.totalMemory=%d%s, runtime.freeMemory=%d%s," +
" runtime.usedMemory=%d%s, runTime.availableMemory=%d%s, freeHeapPercentage=%.2f";
public static void main(String[] args) throws InterruptedException {
final ConcurrentHashMap map = new ConcurrentHashMap();
Runtime runtime = Runtime.getRuntime();
int availableProcessors = runtime.availableProcessors();
int threadCount = availableProcessors * 4;
ArrayList<Thread> threads = new ArrayList<Thread>();
for (int i = 0; i < threadCount; i++) {
threads.add(new Thread(new Runnable() {
@Override
public void run() {
Random random = new Random();
while (true) {
byte[] value = new byte[1024];
random.nextBytes(value);
map.put(random.nextInt(), value);
if (hasReachedMinFreeHeapPercentage(12)) {
break;
}
}
}
}));
}
for (Thread thread : threads) {
thread.start();
}
for (Thread thread : threads) {
thread.join();
}
out.print("\n\n\nEnd of run...now we expect to see actual used-memory value\n");
while (true) {
printCurrentMemoryInfo();
parkNanos(SECONDS.toNanos(5));
}
}
static boolean hasReachedMinFreeHeapPercentage(int minFreeHeapPercentage) {
Runtime runtime = Runtime.getRuntime();
long maxMemory = runtime.maxMemory();
long totalMemory = runtime.totalMemory();
long freeMemory = runtime.freeMemory();
long availableMemory = freeMemory + (maxMemory - totalMemory);
double freeHeapPercentage = 100D * availableMemory / maxMemory;
if (freeHeapPercentage < minFreeHeapPercentage) {
String unit = "M";
out.println(format(MESSAGE, toMB(maxMemory), unit, toMB(totalMemory), unit, toMB(freeMemory), unit,
toMB(totalMemory - freeMemory), unit, toMB(availableMemory), unit, freeHeapPercentage));
return true;
}
return false;
}
static void printCurrentMemoryInfo() {
Runtime runtime = Runtime.getRuntime();
long maxMemory = runtime.maxMemory();
long totalMemory = runtime.totalMemory();
long freeMemory = runtime.freeMemory();
long availableMemory = freeMemory + (maxMemory - totalMemory);
double freeHeapPercentage = 100D * availableMemory / maxMemory;
String unit = "M";
out.println(format(MESSAGE, toMB(maxMemory), unit, toMB(totalMemory), unit, toMB(freeMemory), unit,
toMB(totalMemory - freeMemory), unit, toMB(availableMemory), unit, freeHeapPercentage));
}
static int toMB(long bytes) {
return (int) Math.rint(bytes / MB);
}
}
</pre>
<p style="color:rgb(0,0,0);font-size:12.8px">Java version:</p>
<p style="color:rgb(0,0,0);font-size:12.8px">openjdk version
"1.8.0_91"<br>
</p>
<p style="color:rgb(0,0,0);font-size:12.8px">OpenJDK Runtime
Environment (build 1.8.0_91-8u91-b14-0ubuntu4~14.04-b14)</p>
<p style="color:rgb(0,0,0);font-size:12.8px">OpenJDK 64-Bit
Server VM (build 25.91-b14, mixed mode)</p>
<div style="color:rgb(0,0,0);font-size:12.8px"><br>
</div>
<div style="color:rgb(0,0,0);font-size:12.8px">OS info:</div>
<p style="color:rgb(0,0,0);font-size:12.8px">Linux version
3.13.0-74-generic (buildd@lcy01-07) (gcc version 4.8.2 (Ubuntu
4.8.2-19ubuntu1) ) #118-Ubuntu SMP Thu Dec 17 22:52:10 UTC
2015</p>
<p style="color:rgb(0,0,0);font-size:12.8px">Distributor ID:
Ubuntu</p>
<p style="color:rgb(0,0,0);font-size:12.8px">Description: Ubuntu
14.04.3 LTS</p>
<p style="color:rgb(0,0,0);font-size:12.8px">Release: 14.04</p>
<p style="color:rgb(0,0,0);font-size:12.8px"><br>
</p>
<p style="color:rgb(0,0,0);font-size:12.8px">Thanks in advance,</p>
<div><br>
</div>
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</blockquote>
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