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Full Discussion: Performance issue!
Top Forums UNIX for Advanced & Expert Users Performance issue! Post 302297911 by mavens on Monday 16th of March 2009 06:20:23 AM
Old 03-16-2009
Question Performance issue!

In my C program i am using very large file(approx 400MB) to read parts of it frequently. But due to large file the performance of the program goes down very badly. It shows very high I/O usage and I/O wait time.

My question is, What are the ways to optimize or tune I/O on linux or how i can get better performance when i have to read a large flat file?

I am using
Red Hat Enterprise Linux ES release 4 (Nahant Update 4)
2.6.9-42.EL, x86_64 GNU/Linux
 

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vxfs_bc_bufhwm(5)						File Formats Manual						 vxfs_bc_bufhwm(5)

NAME
vxfs_bc_bufhwm - VxFS buffer cache high water mark(determines the VxFS buffer cache size) SYNOPSIS
VALUE
Specify an integer value. Minimum 6144 KB Maximum None Default 0 DESCRIPTION
VxFS maintains a buffer cache in the kernel for frequently accessed file system metadata in addition to the HP-UX kernel buffer cache that caches the file data. tunable parameter determines the size of the VxFS buffer cache (the maximum amount of memory that can be used to cache VxFS metadata). The default value computed based on the amount of system memory ensures good system performance across a wide range of applications. The value of is specified in kilobytes. To improve performance during application loads that cause frequent file system metadata changes on the system (for example, a high rate of file creation or deletion, or accessing large directories), change the value of Notes Use the command to monitor buffer cache statistics and inode cache usage. EXAMPLES
Set the maximum of size of buffer cache at 300000: WARNINGS
All HP-UX kernel tunable parameters are release specific. This parameter may be removed or its meaning may change in the future releases of HP-UX. Installation of optional kernel software, from HP or other vendors, may cause changes to tunable parameter values. After installation, some tunable parameters may no longer be at the default or recommended values. For information about the effects of installation on tun- able values, consult the documentation for the kernel software being installed. For information about optional kernel software that was factory installed on your system, see at SEE ALSO
kctune(1M), vxfsstat(1M), vx_maxlink(5), vx_ninode(5), vxfs_ifree_timelag(5). Tunable Kernel Parameters vxfs_bc_bufhwm(5)
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