topic Re: buffer cache in Operating System - HP-UX

buffer cache

I.Delic — Fri, 14 Nov 2003 07:00:29 GMT

Hi,

Who can i check the size of buffer cashe on unix 11.11i
Every answer about this subject is welcom

Thank you

Re: buffer cache

Jean-Luc Oudart — Fri, 14 Nov 2003 07:06:42 GMT

If you have Glance installed on the system,
use "m" for memory report.

Rgds,
Jean-Luc

Re: buffer cache

I.Delic — Fri, 14 Nov 2003 07:12:51 GMT

Hi,
I don't have glance

Idriz

Re: buffer cache

Trond Haugen — Fri, 14 Nov 2003 07:16:49 GMT

If you don't have Glance you can see how manny 4k pages is in use by running rhis command:
echo bufpages/D | adb -k /stand/vmunix /dev/kmem

Regards,
Trond

Re: buffer cache

Jean-Luc Oudart — Fri, 14 Nov 2003 07:21:41 GMT

# kmtune | grep -i dbc_max_pct
dbc_max_pct 15
# kmtune | grep -i bufpages
bufpages 78643
#

If bufpages is non-zero you will have a fix buffer size (given in 4Kb pages) otherwise check your dbc_mac_pct it will give you tha maximum % of your real memory dedicated to buffer cache.
Default is far too high and should be tuned.

Rgds,
Jean-Luc

Re: buffer cache

Laurent Menase — Fri, 14 Nov 2003 07:21:58 GMT

adb /stand/vmunix /dev/kmem <dbc_max_pct/D
dbc_min_pct/D
bufpages/D
dbc_ceiling/D
dbc_bufpages/D

Re: buffer cache

Jean-Luc Oudart — Fri, 14 Nov 2003 07:23:26 GMT

Check this previous thread about tuning your buffer cache

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=115045

Rgds,
Jean-Luc

Re: buffer cache

Lee Huei — Mon, 17 Nov 2003 04:47:10 GMT

size of buffer cache on hpux 11i:

check on physical memory size from dmesg
eg:
Physical: 131072 Kbytes -> 128Mbytes

check kernel parameter to see if you are using static buffer or dynamic buffer cache.
*note* dynamic buffer cahche is desirable.

if nbuf=0 then you are using dynamic buffer cache
eg:
bufpages ( NBUF*2)
nbuf 0

check the dynamic buffer cahche value
(a)dbc_min_pct
(b)dbc_max_pct
eg:
dbc_min_pct 5
dbc_max_pct 15

then, the buffer cache allocated is:
minimum of 6.4 Mbytes
maximum of 19.2Mbytes

It is recommended to always keep buffer cache size lower than 300mbytes.

Re: buffer cache

Geoff Wild — Mon, 17 Nov 2003 16:50:36 GMT

Run this command:

/usr/contrib/Q4/bin/kmeminfo

Looks like:

kmeminfo (3.11)
libp4 (5.17): Opening /stand/vmunix /dev/kmem

Loading symbols from /stand/vmunix

======================================================================
Date: Mon Nov 17 14:49:06 2003

Processing pfdat table (2505108 entries)...

----------------------------------------------------------------------
Physical memory usage summary (in pages):

Physmem = 2580480 Available physical memory:
Freemem = 704683 Free physical memory
Used = 1875797 Used physical memory:
System = 333474 by kernel:
Static = 75372 for text and static data
Dynamic = 0 for dynamic data
Bufcache = 258048 for file-system buffer cache
Eqmem = 54 for equiv. mapped page pool
SCmem = 0 for system critical page pool
User = 1052279 by user processes
Uarea = 8096 for thread uareas
Disowned = 63983 disowned pages

----------------------------------------------------------------------
Dynamic memory usage summary (in pages):

Dynamic = 0 Kernel dynamic data (sysmap):
MALLOC = 0 memory buckets:
bucket[ 5] = 0 size 32 bytes
bucket[ 6] = 0 size 64 bytes
bucket[ 7] = 0 size 128 bytes
bucket[ 8] = 0 size 256 bytes
bucket[ 9] = 0 size 512 bytes
bucket[10] = 0 size 1024 bytes
bucket[11] = 0 size 2048 bytes
bucket[12] = 0 size 4096 bytes
bucket[13] = 0 size 2 pages
bucket[14] = 0 size 3 pages
bucket[15] = 0 size 4 pages
bucket[16] = 0 size 5 pages
bucket[17] = 0 size 6 pages
bucket[18] = 0 size 7 pages
bucket[19] = 0 size 8 pages
bucket[20] = 0 size > 8 pages
Kalloc = 0 kalloc()
Eqalloc = 0 eqalloc()
Reserved = 0 Reserved pools

Rgds...Geoff