Page 1 of 1

cycles cpu rendering - a question of memory usage

Posted: Sat May 04, 2013 9:15 am
by farbw3rk
hi,

simple question: *not thinking about performance*, will a big scene rendered in cycles make usage of systems swap if systems memory isn't big enough? in my opinion the kernel would deal with it, so blender could use mem+swap when needed.

not talking about GPU-rendering, cycles cpu-render only. platform: linux x64.

maybe i'm too stupid to search, but i hadn't found an answer while searching the forum, sorry.

Posted: Sat May 04, 2013 4:57 pm
by stiv
As long as you have a swap file, a modern OS will use it if an application needs more memory.

You can still run out of memory on a 32 bit system because the processor can only address about 4 gigabytes of memory.

Posted: Sat May 04, 2013 7:08 pm
by farbw3rk
[quote="stiv"]As long as you have a swap file, a modern OS will use it if an application needs more memory.

You can still run out of memory on a 32 bit system because the processor can only address about 4 gigabytes of memory.[/quote]

thanks for the reply.
i know about the (soft) 4GB limit per 32bit OS - anyway, processlimit in 32bit OS is 2GB (in java 1.5gb heap max btw. - *sigh, i hate it*). no point here, as i run my farm on 64bit linux.
applications deal different with swapped memory. as i said, the kernel would deal with it, but does blender act stable in swapping conditions?

Posted: Sun May 05, 2013 4:50 pm
by stiv
Blender does not mind if your system starts paging, but you might since disk I/O is so much slower than straight memory access.

Where things break down is when Blender asks for a big chunk of memory and the OS replies, "sorry. cannot find a contiguous chunk that big". This leads to forum threads where someone says Blender crashed but I still (seem to) have lots of memory.

Posted: Sun May 05, 2013 6:04 pm
by farbw3rk
nodes are booting over nfs but swap is on a 7200rpm local SATA-device, so IO would be ok, to speak for swapped memory. as said, i don't mind when performance would slow down on bigger scenes/frames when system comes to paging, as long as blender keeps stable.