Linux – How to see top processes sorted by actual memory usage

linuxmemoryopensuseram

I have a server with 12G of memory. A fragment of top is shown below:

PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                                                                                                                                                                                                                                      
12979 frank  20   0  206m  21m  12m S   11  0.2  26667:24 krfb                                                                                                                                                                                                                                                          
13 root      15  -5     0    0    0 S    1  0.0  36:25.04 ksoftirqd/3                                                                                                                                                                                                                                                   
59 root      15  -5     0    0    0 S    0  0.0   4:53.00 ata/2                                                                                                                                                                                                                                                         
2155 root      20   0  662m  37m 8364 S    0  0.3 338:10.25 Xorg                                                                                                                                                                                                                                                          
4560 frank  20   0  8672 1300  852 R    0  0.0   0:00.03 top                                                                                                                                                                                                                                                           
12981 frank  20   0  987m  27m  15m S    0  0.2  45:10.82 amarok                                                                                                                                                                                                                                                        
24908 frank  20   0 16648  708  548 S    0  0.0   2:08.84 wrapper                                                                                                                                                                                                                                                       
1 root      20   0  8072  608  572 S    0  0.0   0:47.36 init                                                                                                                                                                                                                                                          
2 root      15  -5     0    0    0 S    0  0.0   0:00.00 kthreadd

The free -m shows the following:

             total       used       free     shared    buffers     cached
Mem:         12038      11676        362          0        599       9745
-/+ buffers/cache:       1331      10706
Swap:         2204        257       1946

If I understand correctly, the system has only 362 MB of available memory. My question is: How can I find out which process is consuming most of the memory?

Just as background info, the system is running 64bit OpenSuse 12.

Best Answer

use quick tip using top command in linux/unix

$ top

and then hit Shift+m (i.e. write a capital M).

From man top

SORTING of task window
  For compatibility, this top supports most of the former top sort keys.
  Since this is primarily a service to former top users, these commands do
  not appear on any help screen.
    command   sorted-field                  supported
      A         start time (non-display)      No
      M         %MEM                          Yes
      N         PID                           Yes
      P         %CPU                          Yes
      T         TIME+                         Yes

Or alternatively: hit Shift + f , then choose the display to order by memory usage by hitting key n then press Enter. You will see active process ordered by memory usage

Windows

Some of the above values are easily available from the appropriate Win32 API, I just list them here for completeness. Others, however, need to be obtained from the Performance Data Helper library (PDH), which is a bit "unintuitive" and takes a lot of painful trial and error to get to work. (At least it took me quite a while, perhaps I've been only a bit stupid...)

Note: for clarity all error checking has been omitted from the following code. Do check the return codes...!

Total Virtual Memory:
```
#include "windows.h"

MEMORYSTATUSEX memInfo;
memInfo.dwLength = sizeof(MEMORYSTATUSEX);
GlobalMemoryStatusEx(&memInfo);
DWORDLONG totalVirtualMem = memInfo.ullTotalPageFile;
```
Note: The name "TotalPageFile" is a bit misleading here. In reality this parameter gives the "Virtual Memory Size", which is size of swap file plus installed RAM.

Virtual Memory currently used:

Same code as in "Total Virtual Memory" and then

 DWORDLONG virtualMemUsed = memInfo.ullTotalPageFile - memInfo.ullAvailPageFile;

Virtual Memory currently used by current process:

#include "windows.h"
#include "psapi.h"

PROCESS_MEMORY_COUNTERS_EX pmc;
GetProcessMemoryInfo(GetCurrentProcess(), (PROCESS_MEMORY_COUNTERS*)&pmc, sizeof(pmc));
SIZE_T virtualMemUsedByMe = pmc.PrivateUsage;

Total Physical Memory (RAM):

Same code as in "Total Virtual Memory" and then
```
DWORDLONG totalPhysMem = memInfo.ullTotalPhys;
```
Physical Memory currently used:

Same code as in "Total Virtual Memory" and then
```
DWORDLONG physMemUsed = memInfo.ullTotalPhys - memInfo.ullAvailPhys;
```
Physical Memory currently used by current process:

Same code as in "Virtual Memory currently used by current process" and then
```
SIZE_T physMemUsedByMe = pmc.WorkingSetSize;
```

CPU currently used:

#include "TCHAR.h"
#include "pdh.h"

static PDH_HQUERY cpuQuery;
static PDH_HCOUNTER cpuTotal;

void init(){
    PdhOpenQuery(NULL, NULL, &cpuQuery);
    // You can also use L"\\Processor(*)\\% Processor Time" and get individual CPU values with PdhGetFormattedCounterArray()
    PdhAddEnglishCounter(cpuQuery, L"\\Processor(_Total)\\% Processor Time", NULL, &cpuTotal);
    PdhCollectQueryData(cpuQuery);
}

double getCurrentValue(){
    PDH_FMT_COUNTERVALUE counterVal;

    PdhCollectQueryData(cpuQuery);
    PdhGetFormattedCounterValue(cpuTotal, PDH_FMT_DOUBLE, NULL, &counterVal);
    return counterVal.doubleValue;
}

CPU currently used by current process:

#include "windows.h"

static ULARGE_INTEGER lastCPU, lastSysCPU, lastUserCPU;
static int numProcessors;
static HANDLE self;

void init(){
    SYSTEM_INFO sysInfo;
    FILETIME ftime, fsys, fuser;

    GetSystemInfo(&sysInfo);
    numProcessors = sysInfo.dwNumberOfProcessors;

    GetSystemTimeAsFileTime(&ftime);
    memcpy(&lastCPU, &ftime, sizeof(FILETIME));

    self = GetCurrentProcess();
    GetProcessTimes(self, &ftime, &ftime, &fsys, &fuser);
    memcpy(&lastSysCPU, &fsys, sizeof(FILETIME));
    memcpy(&lastUserCPU, &fuser, sizeof(FILETIME));
}

double getCurrentValue(){
    FILETIME ftime, fsys, fuser;
    ULARGE_INTEGER now, sys, user;
    double percent;

    GetSystemTimeAsFileTime(&ftime);
    memcpy(&now, &ftime, sizeof(FILETIME));

    GetProcessTimes(self, &ftime, &ftime, &fsys, &fuser);
    memcpy(&sys, &fsys, sizeof(FILETIME));
    memcpy(&user, &fuser, sizeof(FILETIME));
    percent = (sys.QuadPart - lastSysCPU.QuadPart) +
        (user.QuadPart - lastUserCPU.QuadPart);
    percent /= (now.QuadPart - lastCPU.QuadPart);
    percent /= numProcessors;
    lastCPU = now;
    lastUserCPU = user;
    lastSysCPU = sys;

    return percent * 100;
}

Linux

On Linux the choice that seemed obvious at first was to use the POSIX APIs like getrusage() etc. I spent some time trying to get this to work, but never got meaningful values. When I finally checked the kernel sources themselves, I found out that apparently these APIs are not yet completely implemented as of Linux kernel 2.6!?

In the end I got all values via a combination of reading the pseudo-filesystem /proc and kernel calls.

Total Virtual Memory:

#include "sys/types.h"
#include "sys/sysinfo.h"

struct sysinfo memInfo;

sysinfo (&memInfo);
long long totalVirtualMem = memInfo.totalram;
//Add other values in next statement to avoid int overflow on right hand side...
totalVirtualMem += memInfo.totalswap;
totalVirtualMem *= memInfo.mem_unit;

Virtual Memory currently used:

Same code as in "Total Virtual Memory" and then

long long virtualMemUsed = memInfo.totalram - memInfo.freeram;
//Add other values in next statement to avoid int overflow on right hand side...
virtualMemUsed += memInfo.totalswap - memInfo.freeswap;
virtualMemUsed *= memInfo.mem_unit;

Virtual Memory currently used by current process:

#include "stdlib.h"
#include "stdio.h"
#include "string.h"

int parseLine(char* line){
    // This assumes that a digit will be found and the line ends in " Kb".
    int i = strlen(line);
    const char* p = line;
    while (*p <'0' || *p > '9') p++;
    line[i-3] = '\0';
    i = atoi(p);
    return i;
}

int getValue(){ //Note: this value is in KB!
    FILE* file = fopen("/proc/self/status", "r");
    int result = -1;
    char line[128];

    while (fgets(line, 128, file) != NULL){
        if (strncmp(line, "VmSize:", 7) == 0){
            result = parseLine(line);
            break;
        }
    }
    fclose(file);
    return result;
}

Total Physical Memory (RAM):

Same code as in "Total Virtual Memory" and then

long long totalPhysMem = memInfo.totalram;
//Multiply in next statement to avoid int overflow on right hand side...
totalPhysMem *= memInfo.mem_unit;

Physical Memory currently used:

Same code as in "Total Virtual Memory" and then

long long physMemUsed = memInfo.totalram - memInfo.freeram;
//Multiply in next statement to avoid int overflow on right hand side...
physMemUsed *= memInfo.mem_unit;

Physical Memory currently used by current process:

Change getValue() in "Virtual Memory currently used by current process" as follows:

int getValue(){ //Note: this value is in KB!
    FILE* file = fopen("/proc/self/status", "r");
    int result = -1;
    char line[128];

    while (fgets(line, 128, file) != NULL){
        if (strncmp(line, "VmRSS:", 6) == 0){
            result = parseLine(line);
            break;
        }
    }
    fclose(file);
    return result;
}

CPU currently used:

#include "stdlib.h"
#include "stdio.h"
#include "string.h"

static unsigned long long lastTotalUser, lastTotalUserLow, lastTotalSys, lastTotalIdle;

void init(){
    FILE* file = fopen("/proc/stat", "r");
    fscanf(file, "cpu %llu %llu %llu %llu", &lastTotalUser, &lastTotalUserLow,
        &lastTotalSys, &lastTotalIdle);
    fclose(file);
}

double getCurrentValue(){
    double percent;
    FILE* file;
    unsigned long long totalUser, totalUserLow, totalSys, totalIdle, total;

    file = fopen("/proc/stat", "r");
    fscanf(file, "cpu %llu %llu %llu %llu", &totalUser, &totalUserLow,
        &totalSys, &totalIdle);
    fclose(file);

    if (totalUser < lastTotalUser || totalUserLow < lastTotalUserLow ||
        totalSys < lastTotalSys || totalIdle < lastTotalIdle){
        //Overflow detection. Just skip this value.
        percent = -1.0;
    }
    else{
        total = (totalUser - lastTotalUser) + (totalUserLow - lastTotalUserLow) +
            (totalSys - lastTotalSys);
        percent = total;
        total += (totalIdle - lastTotalIdle);
        percent /= total;
        percent *= 100;
    }

    lastTotalUser = totalUser;
    lastTotalUserLow = totalUserLow;
    lastTotalSys = totalSys;
    lastTotalIdle = totalIdle;

    return percent;
}

CPU currently used by current process:

#include "stdlib.h"
#include "stdio.h"
#include "string.h"
#include "sys/times.h"
#include "sys/vtimes.h"

static clock_t lastCPU, lastSysCPU, lastUserCPU;
static int numProcessors;

void init(){
    FILE* file;
    struct tms timeSample;
    char line[128];

    lastCPU = times(&timeSample);
    lastSysCPU = timeSample.tms_stime;
    lastUserCPU = timeSample.tms_utime;

    file = fopen("/proc/cpuinfo", "r");
    numProcessors = 0;
    while(fgets(line, 128, file) != NULL){
        if (strncmp(line, "processor", 9) == 0) numProcessors++;
    }
    fclose(file);
}

double getCurrentValue(){
    struct tms timeSample;
    clock_t now;
    double percent;

    now = times(&timeSample);
    if (now <= lastCPU || timeSample.tms_stime < lastSysCPU ||
        timeSample.tms_utime < lastUserCPU){
        //Overflow detection. Just skip this value.
        percent = -1.0;
    }
    else{
        percent = (timeSample.tms_stime - lastSysCPU) +
            (timeSample.tms_utime - lastUserCPU);
        percent /= (now - lastCPU);
        percent /= numProcessors;
        percent *= 100;
    }
    lastCPU = now;
    lastSysCPU = timeSample.tms_stime;
    lastUserCPU = timeSample.tms_utime;

    return percent;
}

TODO: Other Platforms

I would assume, that some of the Linux code also works for the Unixes, except for the parts that read the /proc pseudo-filesystem. Perhaps on Unix these parts can be replaced by getrusage() and similar functions?

Linux – How to measure the actual memory usage of an application or process

With ps or similar tools you will only get the amount of memory pages allocated by that process. This number is correct, but:

does not reflect the actual amount of memory used by the application, only the amount of memory reserved for it
can be misleading if pages are shared, for example by several threads or by using dynamically linked libraries

If you really want to know what amount of memory your application actually uses, you need to run it within a profiler. For example, Valgrind can give you insights about the amount of memory used, and, more importantly, about possible memory leaks in your program. The heap profiler tool of Valgrind is called 'massif':

Massif is a heap profiler. It performs detailed heap profiling by taking regular snapshots of a program's heap. It produces a graph showing heap usage over time, including information about which parts of the program are responsible for the most memory allocations. The graph is supplemented by a text or HTML file that includes more information for determining where the most memory is being allocated. Massif runs programs about 20x slower than normal.

As explained in the Valgrind documentation, you need to run the program through Valgrind:

valgrind --tool=massif <executable> <arguments>

Massif writes a dump of memory usage snapshots (e.g. massif.out.12345). These provide, (1) a timeline of memory usage, (2) for each snapshot, a record of where in your program memory was allocated. A great graphical tool for analyzing these files is massif-visualizer. But I found ms_print, a simple text-based tool shipped with Valgrind, to be of great help already.

To find memory leaks, use the (default) memcheck tool of valgrind.

Best Answer

Related Solutions

C++ – How to determine CPU and memory consumption from inside a process

Windows

Linux

TODO: Other Platforms

Linux – How to measure the actual memory usage of an application or process

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