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Physical memory usage of kernel

 
Highlighted
Regular Advisor

Physical memory usage of kernel

Hi there,

I have two rx4640, with install 16GB of Physical memory. The same OS version but the physical memory usage of kernel are different via kmeminfo command.

Server 1 :
=========
Physical memory usage summary (in page/byte/percent):

Physical memory = 4189222 16.0g 100%
Free memory = 1795653 6.8g 43%
User processes = 1682435 6.4g 40% details with -user
System = 695314 2.7g 17%
Kernel = 485852 1.9g 12% kernel text and data
Dynamic Arenas = 199482 779.2m 5% details with -arena
vx_inode_cache = 43323 169.2m 1%
vx_global_pool = 34866 136.2m 1%
spinlock = 24388 95.3m 1%
vx_buffer_cache = 17888 69.9m 0%
vm_pfn2v_arena = 16566 64.7m 0%
Other arenas = 62451 243.9m 1% details with -arena
Super page pool = 20010 78.2m 0% details with -kas
Static Tables = 200994 785.1m 5% details with -static
pfdat = 98184 383.5m 2%
nbuf = 45824 179.0m 1% bufcache headers
vhpt = 32768 128.0m 1%
bufhash = 8192 32.0m 0% bufcache hash headers
text = 7389 28.9m 0% vmunix text section
Other tables = 8636 33.7m 0% details with -static
Buffer cache = 209462 818.2m 5% details with -bufcache

Server 2:
=========
Physical memory usage summary (in page/byte/percent):

Physical memory = 2092068 8.0g 100%
Free memory = 923798 3.5g 44%
User processes = 779572 3.0g 37% details with -user
System = 375567 1.4g 18%
Kernel = 270963 1.0g 13% kernel text and data
Dynamic Arenas = 82796 323.4m 4% details with -arena
vx_global_pool = 18910 73.9m 1%
spinlock = 11721 45.8m 1%
vm_pfn2v_arena = 8406 32.8m 0%
VFD_BT_NODE = 5242 20.5m 0%
vx_inode_cache = 4246 16.6m 0%
Other arenas = 34271 133.9m 2% details with -arena
Super page pool = 24050 93.9m 1% details with -kas
Static Tables = 119341 466.2m 6% details with -static
pfdat = 49032 191.5m 2%
nbuf = 35184 137.4m 2% bufcache headers
vhpt = 16384 64.0m 1%
text = 7544 29.5m 0% vmunix text section
bufhash = 4096 16.0m 0% bufcache hash headers
Other tables = 7100 27.7m 0% details with -static
Buffer cache = 104604 408.6m 5% details with -bufcache

How come the kernel text and data in server 1 greater than server 2?

I hope that you can help me.

Thanks
4 REPLIES 4
Highlighted
Regular Advisor

Re: Physical memory usage of kernel

sorry, server 2 has 8GB and server 1 has 16GB
Highlighted
Acclaimed Contributor

Re: Physical memory usage of kernel

HI:

Fisrt, it would seem that server-1 has 16GB physical memory whereas server-2 has 8GB.

Regardless, server-1 shows about 12% kernel text and data whereas server-2 shows 13%.

Do you really consider that a difference? I certainly don't. I presume too, that these servers were booted at different times and have undergone different work loads since. You aren't comparing fairly from that standpoint, then, either.

Regards!

...JRF...
Highlighted
Honored Contributor

Re: Physical memory usage of kernel

Text? All I can think is a different driver module on one vs. another. The tiny difference you're talking about would only entice me to track it down if I truly had nothing better to do with my life.

Data -- Well, first there's the data that is memory descriptor (pfn-to-virt entries, physical frame descriptors (pfdats)). Those are allocated per memory page... so more memory pages, more of them. (Hence they stay a flat percentage cost but you're trying to look at the raw costs.)

Other than that -- the rest is dynamic data differences. Dynamic being dynamic... it would be a function of the load. I really don't see anything odd here.
Highlighted
Honored Contributor

Re: Physical memory usage of kernel

As Don mentioned there are a number of kernel configs that are dynamic in nature and allocated at time of boot. Examples that comes to mind is the min_dbc_pct/max_dbc_pct another example is vx_ninode. I am sure there are 100s of others.

So unless you hard code every one of these your mileage will vary. Especially when % of 16GB or 8GB are involved.