Memory Leak

[Hongwei Li]

> Hongwei Li wrote:
>>>On Thu, Feb 10, 2005 at 10:15:39AM +0100, DafyddHugh wrote:
>>> > Hi,
>>> >
>>> > I am running Fedora Core 3 on a machine with 512Mb memory.
>>> >
>>> > There are 2 problems
>>> >
>>> > 1. When the physical memory is exhausted the system tries to use
>>> swap,
>>>the disk spins and the system becomes unusable. This is under
>>>investigation, but any ideas would be appreciated.
>>> >
>>> > 2. More of an issue. Every few minutes (4 or 5) the available
>>> physical
>>>memory decreases by 64k, while the cache memory increases by 4k or 8k.
>>>This is happening on a very "lean" machine (see simple ps post below).
>>>No processes seem to be increasing memory at the same time. Usually the
>>>machine also runs httpd, mysqld, popfile in addition to the posted ps.
>>>It looks like a memory leak, but I can't find the offending process -
>>>any ideas?
>>>
>>>Which kernel version are you running ?
>>>What does the output of free, and slabtop look like ?
>>>
>>>		Dave
>>
>>
>> I have a similar question as 2 above.  My system: 2.6.10-1.741_FC3
>> The free command displays the free physical memory decreasing
>> continuesly
>> every minute or so:
>>
>> # free
>>              total       used       free     shared    buffers
>> cached
>> Mem:       1035788    1017952      17836          0     296172
>> 81224
>> -/+ buffers/cache:     640556     395232
>> Swap:      1052216       8120    1044096
>>
>> # free
>>              total       used       free     shared    buffers
>> cached
>> Mem:       1035788    1017980      17808          0     296228
>> 81244
>> -/+ buffers/cache:     640508     395280
>> Swap:      1052216       8120    1044096
>>
>> # free
>>              total       used       free     shared    buffers
>> cached
>> Mem:       1035788    1018100      17688          0     296260
>> 81300
>> -/+ buffers/cache:     640540     395248
>> Swap:      1052216       8120    1044096
>>
>> Is it normal?  I don't know what will happen if the free memory goes to
>> zero, but it seems that, in my system, it never goes to zero.  At some
>> point, it jumps up a little.  Please note, my this system is a testing
>> system, only 2 regular users were set up, and only 1 user is checking
>> the
>> testing emails (plus root's shell).  It was just rebooted 2 days ago:
>>
>> # top
>> top - 11:51:21 up 1 day, 21:36,  3 users,  load average: 0.00, 0.00,
>> 0.00
>> Tasks:  90 total,   1 running,  86 sleeping,   0 stopped,   3 zombie
>> Cpu(s):  0.3% us,  0.0% sy,  0.0% ni, 99.3% id,  0.0% wa,  0.3% hi,
>> 0.0% si
>> Mem:   1035788k total,  1018564k used,    17224k free,   296420k buffers
>> Swap:  1052216k total,     8120k used,  1044096k free,    81360k cached
>>
>>   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
>> 10847 root      16   0  3632  948  756 R  0.7  0.1   0:00.07 top
>>  3438 root      16   0  3940  580  492 S  0.3  0.1   0:17.43 nifd
>>  3938 root      16   0  7756 4848 1612 S  0.3  0.5   1:11.28 hald
>>     1 root      16   0  2756  560  480 S  0.0  0.1   0:00.82 init
>>     2 root      34  19     0    0    0 S  0.0  0.0   0:00.08 ksoftirqd/0
>> ...
>>
>> Why does it take almost all of 1Gb physical ram?
>
> The kernel will attempt to use any available memory for buffering and
> cacheing, as this makes things run faster. When applications need more
> memory, buffer and cache space is released. So the figure you need to
> look at in the "free" output is the one in the row marked "-/+
> buffers/cache:", which shows memory usage not in buffers and cache; that
> represents how much memory you're "really" using. In your example above,
>   the last run of "free" actually showed more free memory than the first
> one.
>
> Paul.
>
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Thank you very much for help!

Hongwei Li