best memory option for java

[paulobreim]

Considering a machine with SSDs, 2 processors with 16 threads each and a large amount of memory (384GB), what is the best option to use in the command line?
java -Xms30G -Xmx30G -jar iped.jar ......
java -jar iped.jar ......
or another?

[mcquadenc]

Hi Paulo,

the documentation says:

IPED used memory increases at processing time if you have dozens of CPU cores (1GB per logical CPU core is a rule of thumb) and at analysis time if your case is huge (for dozens of millions of files you will need a few dozens of GBs). Generally, it is best to let the JVM allocate memory by itself (by default it takes 1/4 of your physical RAM) instead setting it with -Xms/-Xmx, although setting half of your physical RAM is another good rule of thumb

When you say threads, do you mean logical cores!?

barring better judgment, iped allocates up to 1/4 of its memory by default.

with the amount of available memory you have, I think it would be a good alternative to use ramdisk.

[lfcnassif]

You can use this command to check the java defaults on your (Windows) system:
java -XX:+PrintFlagsFinal -version | findstr HeapSize

java -Xms30G -Xmx30G -jar iped.jar ......

I would say those are good default values for most cases given your number of threads/logical cores. Remaining memory would be used as IO cache by your OS, or maybe you could create a ramdrive for temp disk as @mcquadenc suggested, leaving at least the same amount of memory given to the application as free memory/IO cache.

[lfcnassif]

I've just updated this in the wiki:
on most systems java 8 default max heap size is half the RAM and java 9 and newer common default is 1/4 of the RAM

[paulobreim]

Very good.
Here is the result about java defaults:
c:\iped-3.18.14\iped-3.18.14>java -XX:+PrintFlagsFinal -version | findstr HeapSize
uintx ErgoHeapSizeLimit = 0 {product}
uintx HeapSizePerGCThread = 87241520 {product}
uintx InitialHeapSize := 2147483648 {product}
uintx LargePageHeapSizeThreshold = 134217728 {product}
uintx MaxHeapSize := 2145386496 {product}
java version "1.8.0_321"
Java(TM) SE Runtime Environment (build 1.8.0_321-b07)
Java HotSpot(TM) 64-Bit Server VM (build 25.321-b07, mixed mode)

I will try use ramdisk, very goog idea.

Thank you

[lfcnassif]

uintx MaxHeapSize := 2145386496 {product}

See the default java max memory on your system is just 2GB, so you would be better using -Xmx30G

[paulobreim]

Thank you. I will do it.

[jojo-nc]

Considering a machine with SSDs, 2 processors with 16 threads each and a large amount of memory (384GB), what is the best option to use in the command line? java -Xms30G -Xmx30G -jar iped.jar ...... java -jar iped.jar ...... or another?

Arguments -Xms30G and -Xmx30G (or any memory size you want to set) also work with the compiled iped.exe (like -d input_file or -o output_dir)