Re: Mersenne: Torture test allocating hundreds of MB?
On Wednesday 30 October 2002 02:34, Nathan Russell wrote: > > Thanks to everyone who responded. In this case, it's a bug in my > thinking. I had the memory usage set to the max allowable, because I > wanted P-1 to succeed whenever possible, even if it inconvenienced me > - I do most of my academic work via VNC into timeshares, so it isn't a > big deal if the system thrashes. > > Is that the Wrong Thing (tm) to do in terms of improving Prime95's > efficiency? No, in principle its the Right Thing (tm). In practise you want to set the memory parameters big enough that that all available memory is in use, but just small enough that swap thrashing doesn't occur. Because swap thrashing is _so_ limiting to memory access speed, it's best to be on the cautious side - especially since you may occasionally want to do some "real work" on the system. My current practise is as follows: On systems with 128 MB memory, or less, set max memory to half the memory size. (Obviously this is not sane on systems with very small memory ...) On systems with more than 128 MB memory, set max memory to memory size less 80 MB. Except for one system with 512 MB which regularly processes very large files, so I limit mprime to 128 MB to avoid any possibility of the system having to sort files hundreds of megabytes in size in only ~ 40 MBytes real memory. Remember the OS kernel consumes memory too! >From the point of view of "torture testing" a system, again the sane thing is to test as much memory as possible. Causing swap thrashing by setting the memory allocation set a bit too high may be a good way of testing the disk I/O subsystem; however the fact that the processor will be idle waiting for data for a lot of the time may (depending on the CPU, power economy settings in the BIOS etc) allow the CPU to run cooler than it normally would. So, if you're testing out CPU cooling rather than memory problems, setting memory allocation very small (i.e. 8 MB) for the duration of the torture test is probably wise. If you really suspect you have a memory subsystem problem, ideally it's best to use a specialist program like memtest86 which runs without an operating system. You simply can't guarantee to test all memory properly with any program running on a multitasking operating system (unless the basic capability is built into the kernel itself!) Regards Brian Beesley _ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: Torture test allocating hundreds of MB?
At 09:34 PM 10/29/2002 -0500, Nathan Russell wrote: I had the memory usage set to the max allowable, because I wanted P-1 to succeed whenever possible, even if it inconvenienced me - I do most of my academic work via VNC into timeshares, so it isn't a big deal if the system thrashes. Is that the Wrong Thing (tm) to do in terms of improving Prime95's efficiency? Yes, thrashing reduces prime95's throughput. _ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: Torture test allocating hundreds of MB?
On Tue, 29 Oct 2002 23:02:34 -, Daran wrote: >2) To better stress main memory, the torture test will now use up to the >amount of memory specified in the Options/CPU dialog box." > >If you haven't allowed it to use this much memory, then it's a bug, >otherwise its a feature. Thanks to everyone who responded. In this case, it's a bug in my thinking. I had the memory usage set to the max allowable, because I wanted P-1 to succeed whenever possible, even if it inconvenienced me - I do most of my academic work via VNC into timeshares, so it isn't a big deal if the system thrashes. Is that the Wrong Thing (tm) to do in terms of improving Prime95's efficiency? Nathan _ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: Torture test allocating hundreds of MB?
At 02:08 PM 10/28/2002 -0500, Nathan Russell wrote: However, when I tried to run a torture test to verify that everything was okay, I saw Prime95 suddenly allocate over 200 MB of memory for no apparent reason, and the computer began thrashing. Late version 22 executables use lots of memory to run the torture test. It uses the maximum of the daytime and nighttime memory values that you specified in Options/CPU. Since this causes thrashing, I'd reduce those values. If those values are already small then let me know as you've uncovered a bug. _ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Mersenne: Torture test allocating hundreds of MB?
Hi folks, I had some problems with unexpected system crashes after bringing my computer back to school, I think becuase something was knocked out of alignment - it seems to be gone now. However, when I tried to run a torture test to verify that everything was okay, I saw Prime95 suddenly allocate over 200 MB of memory for no apparent reason, and the computer began thrashing. I now just deleted the self-test N complete line in local.ini, and am running a test when I start the program; this appears to be working fine, and the system is stable. I just wonder if the allocating tons of memory is a known issue, or possibly just due to the instability I noted before. I'm using v22.8.1 under win2k sp3. Nathan _ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
