Re: [fpc-pascal] Memory Size
Hi Jonas, > First of all, you set the global system unit variable > 'ReturnNilIfGrowHeapFails' to true, so that instead of a run time > error (or exception) you will simply get nil if a memory allocation > fails. This is a very good tip! I have read about 'ReturnNilIfGrowHeapFails' but I forget it. I think, it is a good solution for my problem. > Secondly, not being able to allocate an array of 2GB is unrelated to > FPC, but due to the fact that you are (most likely) working on a 32 > bit OS. While the theoretical maximum limit for 32 bit systems is 4GB, > it is impossible to ever allocate that much memory in a s single block. Yes, it finally sunk in. I see clearlier the context of memomry management. Thanks. > The reason is that while your program runs in its own virtual memory > space, it is not the only thing in that space. The kernel usually > takes part of the memory (512MB to 1GB), your program code, data and > stack take part of it (and not contiguously; e.g., the code and data > usually start somewhere around address 0x804000, while the stack > starts at 0xC000 and grows downwards from there), and then there > are shared libraries which can be mapped all over the place. Ok, thats new for me. It is very interesting. > As a result, the virtual memory space is fragmented already right > after your program starts, and on most 32 bit systems you seldom can > allocate more than 1.5GB of contiguous memory (simply because other > things are in the way otherwise), and sometimes even less. My experience with the topic coincides with your sentences. Finally, I think i understand some thinks better. Including with your first very good tip, I can fix the problem. Thank you, Jonas, for your help. Also Thank's to Marco. Bye, Markus ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Memory Size
On 04 Apr 2009, at 20:47, Markus Glugla wrote: But, if I allocate 2GB memory the program crashs with an access violation. I have read that fpc can handle arrays up to a size of 2GB, isn't? How great can be an array? First of all, you set the global system unit variable 'ReturnNilIfGrowHeapFails' to true, so that instead of a run time error (or exception) you will simply get nil if a memory allocation fails. Secondly, not being able to allocate an array of 2GB is unrelated to FPC, but due to the fact that you are (most likely) working on a 32 bit OS. While the theoretical maximum limit for 32 bit systems is 4GB, it is impossible to ever allocate that much memory in a s single block. The reason is that while your program runs in its own virtual memory space, it is not the only thing in that space. The kernel usually takes part of the memory (512MB to 1GB), your program code, data and stack take part of it (and not contiguously; e.g., the code and data usually start somewhere around address 0x804000, while the stack starts at 0xC000 and grows downwards from there), and then there are shared libraries which can be mapped all over the place. As a result, the virtual memory space is fragmented already right after your program starts, and on most 32 bit systems you seldom can allocate more than 1.5GB of contiguous memory (simply because other things are in the way otherwise), and sometimes even less. Jonas ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Memory Size
Hi, Am Freitag, den 03.04.2009, 12:39 +0200 schrieb Marco van de Voort: > As Jonas said you first have to define that value in a multitasking > environment. Ok, I have allocate the memory at the program start and it runs fine. It is quick enough yet with memory swaping. But, if I allocate 2GB memory the program crashs with an access violation. I have read that fpc can handle arrays up to a size of 2GB, isn't? How great can be an array? Thanks, Markus ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Memory Size
In our previous episode, Markus Glugla said: > (very very quick) memory as a cache as soon as practicable. I would > cache streams of measurement values (single type, sample rate circa > 32KHz). The measurement program will run on diffrent machines with > diffrent RAM. Depending on the free memory the number of measurement > values or the measurement times are diffrent. The reason to know the > free memory is to decide what or how should I measure. All buffered > prints into a file are to slow and produce underruns. My idea is to >stream the measurement values into an array and write the array on > disk after the measurement. To do this I must know the memory ;-) > > Is there a other way to get the free memory size? As Jonas said you first have to define that value in a multitasking environment. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Memory Size
Hi Jonas, thank you for your answer. > On which OS? Debian 5.0 GNU/Linux (uname -r: 2.6.26-1-686) > Anyway, even if it would return non-zero values, the information would > be next to useless. The reason is that on modern OS'es, available > physical memory is dynamically divided between the disk cache and > applications, with a lower limit on the disk cache. ... > The information provided by GetFPCHeapStatus is only useful to get > statistics about the heap manager, and not to get any information > about the system you are running on. I have misunderstood this. Ok, thank you. > And what happens if you allocate some memory at the start of your program? > What would you expect memavail to report? The current amount of really "free" > memory? > Free + cache? Free + part of cache? Free + non-wired (i.e., swappable) > + part of cache? Free + non-wired + part of cache + swap space? I need the really "free" memory. I would use the maximal available free working memory (no swap or so) because I need a program-internal quick (very very quick) memory as a cache as soon as practicable. I would cache streams of measurement values (single type, sample rate circa 32KHz). The measurement program will run on diffrent machines with diffrent RAM. Depending on the free memory the number of measurement values or the measurement times are diffrent. The reason to know the free memory is to decide what or how should I measure. All buffered prints into a file are to slow and produce underruns. My idea is to stream the measurement values into an array and write the array on disk after the measurement. To do this I must know the memory ;-) Is there a other way to get the free memory size? Thanks Markus ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Memory Size
On 03 Apr 2009, at 02:34, Markus Glugla wrote: I need the available memory (heap). At that time the functions maxavail or memavail did this. I read that I should use GetFPCHeapStatus and other function currently. This functions produce allways zero!! What can I do? What is wrong? I use fpc version 2.2.0 [2008/05/27] for i386. On which OS? And what happens if you allocate some memory at the start of your program? Anyway, even if it would return non-zero values, the information would be next to useless. The reason is that on modern OS'es, available physical memory is dynamically divided between the disk cache and applications, with a lower limit on the disk cache. What would you expect memavail to report? The current amount of really "free" memory? Free + cache? Free + part of cache? Free + non-wired (i.e., swappable) + part of cache? Free + non-wired + part of cache + swap space? The information provided by GetFPCHeapStatus is only useful to get statistics about the heap manager, and not to get any information about the system you are running on. Jonas ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
