- Community Home
- >
- Servers and Operating Systems
- >
- Operating Systems
- >
- Operating System - HP-UX
- >
- Buffer Cache
Categories
Company
Local Language
Forums
Discussions
Forums
- Data Protection and Retention
- Entry Storage Systems
- Legacy
- Midrange and Enterprise Storage
- Storage Networking
- HPE Nimble Storage
Discussions
Discussions
Discussions
Forums
Forums
Discussions
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
- BladeSystem Infrastructure and Application Solutions
- Appliance Servers
- Alpha Servers
- BackOffice Products
- Internet Products
- HPE 9000 and HPE e3000 Servers
- Networking
- Netservers
- Secure OS Software for Linux
- Server Management (Insight Manager 7)
- Windows Server 2003
- Operating System - Tru64 Unix
- ProLiant Deployment and Provisioning
- Linux-Based Community / Regional
- Microsoft System Center Integration
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Community
Resources
Forums
Blogs
- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Printer Friendly Page
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО06-28-2008 12:53 AM
тАО06-28-2008 12:53 AM
I have a Rx7620 server running HP-UX 11.2vi.
I can see from the tool kmeminfo that my buffer cache usage is 4.7GB (29%).
Is there anyway I can find out what data or processes using the buffer cache?
Thanks
Solved! Go to Solution.
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО06-28-2008 12:59 AM
тАО06-28-2008 12:59 AM
Re: Buffer Cache
U can use "top" or "glance" command.
BR/
Yaqub
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО06-28-2008 01:02 AM
тАО06-28-2008 01:02 AM
Re: Buffer Cache
But to my understanding top command gives the physical memory usage of processes.
What I want is a break-up of the buffer cache usage.
Or maybe what you are saying is the processes that are using the physical memory most are also using the buffer cache?
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО06-28-2008 01:06 AM
тАО06-28-2008 01:06 AM
SolutionBuffer cache is an area of memory between disk and OS. If you don't change any setting it's adjusted so that it can grow up to %50 of memory. Practically this is waste of memory.
dbx_max_pct and dbc_min_pct are kernel parameter you want to set. a common idea is setting these values to:
dbc_max_pct = 5
dbc_min_pct = 2
so it grow up to %5 of memory. You can analyz buffer cache utulization with sar -d command.
Kenan.
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО06-28-2008 09:58 AM
тАО06-28-2008 09:58 AM
Re: Buffer Cache
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО06-28-2008 10:07 AM
тАО06-28-2008 10:07 AM
Re: Buffer Cache
dbc_max_pct
dbc_min_pct
depends upon your physical memory size. for large physical memory you better to use the mentioned values above but for minimum memory this is not fruitful.
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО06-29-2008 12:43 PM
тАО06-29-2008 12:43 PM
Re: Buffer Cache
Example 2 GB of buffer cache hit rate 90%
2.5 gb buffer cache hit rate 95%
3 gb buffer cache hit rate 95%
optimal buffer cache size is 2.5 bg based on the files and blocks of files processes are using.
Good luck.
With 11.31 all bets are off we now have unified file cache.
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО06-29-2008 05:11 PM
тАО06-29-2008 05:11 PM
Re: Buffer Cache
dbc_max_pct - the maximum percentage of memory to be used by dynamic buffer cache.
Values:-
Minimum--->2; Maximun--->90; Default--->50
DESCRIPTION:-
When the parameters bufpages and nbuf are both set to their default value of 0, the size of the buffer cache grows or shrinks dynamically, depending on competing requests for system memory.
The value of dbc_max_pct sets the maximum percentage of physical memory that can be allocated tothe dynamic buffer cache.
It is possible to set both dbc_max_pct and dbc_min_pct to the same value, 12 for example, andcreate a kernel that uses exactly that percentage of physical memory for the buffer cache, regardless of the size of physical memory.
Related Parameters:-
dbc_max_pct must be greater than or equal to dbc_min_pct.
To use dynamic buffer caching, bufpages and nbuf must both be set to zero.
dbc_min_pct - the minimum percentage of memory to be used by the dynamic buffer cache.
Values:-
Minimum--->2; Maximun--->90; Default--->50
DESCRIPTION:-
During file-system I/O operations, data is stored in a buffer cache, the size of which can be fixed or dynamically allocated. When the parameters bufpages and nbuf are both set to their default values of 0, the size of the buffer cache grows or shrinks dynamically, depending on competing requests for system memory.
The value of dbc_min_pct specifies the minimum percentage of physical memory that is reserved for use by the dynamic buffer cache.
It is possible to set both dbc_min_pct and dbc_max_pct to the same value, 12 for example, and create a kernel that uses exactly that percentage of physical memory for the buffer cache, regardless of the size of physical memory.
Selecting an Appropriate Value:-
If dbc_min_pct is set to too low a value, very high demand on the buffer cache can effectively hang the system. The is also true when using fixed buffer cache. To determine a reasonable (and conservative)
value for the minimum cache size in megabytes, use the following formula:
(number-of-system-processes)*(largest-file-system-block-size)/1024
To determine the value for dbc_min_pct, divide the result by the number of megabytes of physical memory installed in the computer and multiply that value by 100 to obtain the correct value in percent.
Only those processes that actively use disk I/O should be included in the calculation. All others can be excluded. Here are some examples of what processes should be included in or excluded from the calculation:
a) Include:-
NFS daemons, text formatters such as nroff, database management applications, text editors, compilers, and so on, that access or use source and/or output files stored in one or more file systems mounted on the system.
b)Exclude:-
X-display applications, hpterm, rlogin, login shells, system daemons, telnet or uucp connections, and so on. These processes use very little, if any, disk I/O.
Related Parameters:-
dbc_min_pct must be less than or equal to dbc_max_pct.
To use dynamic buffer caching, bufpages and nbuf must both be set to zero.
BR/
Yaqub