On Fri, Jan 04, 2008 at 12:09:05AM +0800, Rahul Chopra wrote:
Can you please explain gdk_mem_bigsize and gdk_vm_minsize? I searched around on the site and I am not really clear on what the optimal settings for these are.
Memory blocks allocated via GDKmalloc and friends larger then gdk_mem_bigsize will be mmaped using virtual swap space (vmalloc). This is done to avoid fragmentation.
So this is just for an individual block, and not for total allocated memory? Is a "block" allocated via entire BATs? Or are blocks allocated in segments when read from a single BAT?
BATs have heaps, these can be malloced (GDKmalloc), virtual mmapped using swap space (GDKvmalloc) or mmapped (needs a filename). Blocks (heaps) larger then vm_minsize will be vmalloced. The backends (sql/xquery) control when we switch to mmapped with files.
I am currently using the defaults, on a system with 8 GB of RAM.
It depends on your os if thats okay.
Thanks. I am using Linux (64 bit), CentOS 5.1. My main concern was if setting these too low somehow restricts the amount of memory used and leads to more swapping. I am not familiar enough with the system to understand all of this, but with 8 GB of ram, should I be using a larger gdk_mem_bigsize than the config default of 262144? The config file mentions these being set to 1/2 of available memory, but default values appear commented out. Are those the values that are actually used? Or, if these are commented out, are these dynamically set? -Rahul
Niels
Thanks,
Rahul
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