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Old 2010-10-11, 20:46   #1
lavalamp's Avatar
Oct 2007
Manchester, UK

32·149 Posts
Default GMP-ECM resource usage

Hey there, I have a query about how best to get the most out of my system with very large B2 values in ECM stage 2. I have an i7 CPU with 6 GB of RAM, running Vista 64 bit.

I ran stage 1 in Prime 95, and am using GMP-ECM for stage 2 using the results file as the input, B1=260e6 and B2~=3e12. RAM usage for this B2 value is excessive, so I have been making use of the -k switch to break each curve up into chunks. Since I have a quad core, I tried running 8 instances (2 / core with hyperthreading) and 4 instances (just 1 / core) of GMP-ECM, with B2 bounds that sum to 3e12. For example, these are the B2 bounds I used with -k 62:

Each instance of ECM here uses about 700 MB of RAM maximum, which isn't very much, 4 * 700 = 2800 MB, and I have 6144 MB in total.

I would like to use more RAM so that I can get through the curves quicker, but when I do so it causes the operating system hard drive to grind away constantly, presumably reading and writing metric tons worth of data to the page file. Even at the relatively low RAM usage of 700 MB each, they have all racked up 60 million page faults in just 2 hours.

I wouldn't expect there to be no page faults at all, but surely this value should be 3 or 4 orders of magnitude lower. 2800 MB can easily fit in the RAM with lots of room to spare.

Presumably this is related to how windows is "managing" the memory (wholly ineffectively), so if anyone knows any settings at all that I can tweak to get it to play nice, or if there is a better way to set ECM up that will somehow avoid this constant hard drive assault, I would be very grateful if someone could share it.
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