Controlling the garbage collector (GC) at RT?

Sat Feb 26 20:09:00 GMT 2005

>> You also need to touch the resulting memory. Try something like
>> char *v = sbrk( 1000000 );
>> for (char *p = v; p < p + 1000000; ++p) *p = 42;
>> in the loop.
> I'll try something similar tomorrow, thanks alot - although I will need 
> modify the ever true statement "p < p + 1M" to "p < v + 1M"...
So, now I tried this:
#include <unistd.h>
int main( int i )
{
 while ( 1 ) {
 char *v = sbrk( 1000000 );
 char *p;
 for (*p = v; p < v + 1000000; ++p) {
 *p = 42;
 } // for
 printf( "%x\n\n", v );
 } // while
} // main
And still nothing happens with the memory consumption, although the 
pointer ends up at 0xffffffff...
Weird?!
// Martin
>> I'll return in the morrow...
>> // Martin
>>>> -----Original Message-----
>>> From: java-owner@gcc.gnu.org [mailto:java-owner@gcc.gnu.org] On 
>>> Behalf Of Martin Egholm Nielsen
>>> Sent: Wednesday, February 23, 2005 12:04 AM
>>> To: java@gcc.gnu.org
>>> Subject: Re: Controlling the garbage collector (GC) at RT?
>>>>>>>>>>>>> It seems to me that the only problem here is that this 
>>>>>>>>> still seems to
>>>>>>> happen with overcommit-accounting set to 2.
>>>>>>>>>> I would expect that you can reproduce this problem with a 
>>>>>>>>> program that
>>>>>>> alternately allocates a few MB with sbrk, and then touches the 
>>>> allocated memory. If you can't, there's something really 
>>>>>>>>> weird going
>>>>>>> on here. If you can, it'll give you a test case for the kernel people.
>>>>>>>>> I tried the following:
>>>>>> #include <unistd.h>
>>>>>> int main( int i )
>>> {
>>> while ( 1 ) {
>>> void *v = sbrk( 100000 );
>>> // sleep( 1 );
>>> } // while
>>> } // main
>>>>>> But that doesn't result in anything - the memory usage for the 
>>> application does not grow...
>>> Are there anything else I should do to allocate the memory?
>>>>>> BR,
>>> Martin
>>>>>>>>>> Hans
>>>>>>>> On 2005年2月16日, Martin Egholm Nielsen wrote:
>>>>>>>>>>>>>>>>> Hi Hans,
>>>>>>>>>>>>>>>>>>>>>>> It would indeed be interesting to know why the Linux kernel
>>>>>>>>>>>>>>>>>> kills the application rather than returning failure.
>>>>>>>>>>>>>>>>> Sure, but how to do that? Any guidelines?
>>>>>>>>>>>>>>>>>> What do you see on the console? Anything in the system log? Does 
>>>>>> strace tell you anything?
>>>>>>>>>>>>>>> Below is the last part of "strace -f -F -i -v". It doesn't 
>>>>>>>>> really look
>>>>>>>> like there's anything of value?
>>>>>>>>>> // Martin
>>>>>>>>>> [pid 75] [0f833558] write(1, "*** MEM CHUNK TAKEN: 
>>>>>>>>> 8388608\n", 29***
>>>>>>>> MEM CHUNK TAKEN: 8388608
>>>>> ) = 29
>>>>> [pid 75] [0f839834] brk(0x12d15000) = 0x12d15000
>>>>> [pid 75] [0f839834] brk(0x12d25000) = 0x12d25000
>>>>> [pid 75] [0f81126c] getpid() = 75
>>>>> [pid 75] [0f799444] kill(77, SIGPWR <unfinished ...>
>>>>> [pid 76] [0f840e2c] <... poll resumed> [{fd=3, events=POLLIN,
>>>>> revents=POLLIN}
>>>>> ], 1, 2000) = 1
>>>>> [pid 75] [0f799444] <... kill resumed> ) = 0
>>>>> [pid 76] [0f81127c] getppid() = 75
>>>>> [pid 76] [0f833548] read(3,
>>>>> "20円7円/234円0円0円0円4円17円374円0ドル20円7円/240円$0円0円B17円3円
>>>>> 72j(177円"..., 148) = 148
>>>>> [pid 76] [0f840e2c] poll( <unfinished ...>
>>>>> [pid 75] [0f799444] kill(77, SIGXCPU) = 0
>>>>> [pid 75] [0f839834] brk(0x13525000) = 0x13525000
>>>>> [pid 75] [0f833558] write(1, "*** MEM CHUNK TAKEN: 
>>>>>>>>> 8388608\n", 29***
>>>>>>>> MEM CHUNK TAKEN: 8388608
>>>>> ) = 29
>>>>> [pid 75] [0f839834] brk(0x13535000) = 0x13535000
>>>>> [pid 75] [0f839834] brk(0x13545000) = 0x13545000
>>>>> [pid 75] [0f839834] brk(0x13d45000) = 0x13d45000
>>>>> [pid 75] [0f833558] write(1, "*** MEM CHUNK TAKEN: 
>>>>>>>>> 8388608\n", 29***
>>>>>>>> MEM CHUNK TAKEN: 8388608
>>>>> ) = 29
>>>>> [pid 76] [0f840e2c] <... poll resumed> [{fd=3, 
>>>>>>>>> events=POLLIN}], 1,
>>>>>>>> 2000) = 0
>>>>> [pid 76] [0f840e2c] --- SIGTERM (Terminated) ---
>>>>> #
>>>>>>>>>>>>>>>>>>>>>>>>>