Linux redux - *sigh*

[jkmorse]

So I finally got everything set up and ran my first benchmarks and they blew me away.  These numbers are based on a setup with a 16Gb ramdisk and pointing to it 4 times:

Total:       8310
CPU:        7099
Swap:     28217
Transfer:  5094

Over 5 GB per second!!!  Beats the crap out of anything I tried in Windows.

Best,

Jim

[NGC7789]

That's great! How does the CPU score compare to windows?

If 16GB of swap is not enough consider combining your ramdisk with a source on an SSD. Total swap space is the smallest source times the number of sources (not threads) so adding an SSD to the swap will give you 32GB total. You'll have to experiment with the optimal number of threads per source. I settled on two per source and I wonder if optimal number of swap threads relates to the number of cores.

Consider moving your /tmp to ram rather than declaring a ram disk. It performs about the same and my understanding is that out of memory is handled better with /tmp in ram rather than a ramdisk (although I have seen sources that call /tmp in ram a ramdisk).

Also consider changing your "swappiness". This had a surprising positive impact on PI performance.

For how to do both see this link. It's toward the bottom. I didn't apply the other suggestions on this link. Just swappiness and /tmp to ram.

http://www.skipser.com/p/2/p/speed-up-ubuntu.html

[jkmorse]

With Windows I was under 3 MiB/s so a huge improvement. 

As a newbie to Linux, can you give me a primer on how to point to a Linux-swap partition in PI.  I built two separate 64Gb Linux-swap partitions in two separate SSDs but I cannot for the life of me figure out how to point to those partitions when setting up my swap files.

Thanks,

Jim

[NGC7789]

Linux swap partitions are used by the operating system as the virtual memory scheme. That's why the rule of thumb is to size the swap partition to the amount of ram. So 64gb would be too much if you have 32 gb ram let alone two swap partitions. You can use gparted to remove and resize your swap.

PI swap does not use Linux swap partitions. It uses regular partitions (or folders on regular partitions). Your RAM disk or /tmp is one such. Any SSD or hard disk could be another. Once defined you just point to them in the swap preference panel

[jkmorse]

Just tried subbing out /tmp for /ramdisk and things slowed way way down to under 2 Gb per sec.  When I loaded the ramdisk back up it hit 5.4 Gb per sec.  Not sure why, probably because I did it wrong, but will stick with ramdisk as the best option until I get way better at this whole linux thing.

On reflection it has to be because I didn't move the /tmp to Ram but as I said, that will have to wait until I know what I am doing so ramdisk it is for now.