Red Hat APPLICATION STACK 1.1 RELEASE Bedienungsanleitung PDF herunterladen (Seite 11)

Feature Overview

The manageability ofthe releasehas beenimprovedby integrating anumber of publicly

available kernel patches, such as:

• Stephen Tweedie’s Raw I/O patch, which forms the basis for the SGI raw disk I/O

enhancements. This patch is described in “Raw I/O Path Changes” on page 3.

• The Device File System (CONFIG_DEVFS_FS) patch from Richard Gooch. This

patch provides a more consistent naming scheme for hardware and software

devices.Sites that expect toconnect alarge number ofdevices mayﬁnd DEVFSvery

useful in helping to manage them. DEVFS can also provide the traditional Linux

names for devices, for backward compatibility, and is otherwise very compatible

with the rest of the Linux system.

For more information, look for DEVFS at the following URL:

http://oss.sgi.com/projects/

• The sard utility and associated kernel metrics patch for disk trafﬁc analysis. This

patch provides additional diskI/O statistics, usefulfor tuning databaselayouts and

queries.

• The Alan Cox patch for Linux 2.2.10, which contains numerous bugﬁxes and driver

updates.

Performance Improvements

The performance enhancements, enumerated in the preceding section, accelerate the

performance of I/O intensive applications by streamlining the kernel code and data

paths for disk I/O as well as providing larger shared memory segments and a low

overhead interprocess synchronization mechanism.

Raw I/O Path Changes

Current ﬁle-system-based disk I/O requires ﬁxed size I/O operations (typically 1024

bytes) into kernel buffers, then the data is moved from the kernel buffer to the user

program address space. While this allows the ﬁle system to cache frequently accessed

data, it also consumes excess system bus bandwidth when copying the data from the

kernelbuffer(s)into the useraddressspace. Both thesmall sizeof theI/O (2sectors) and

the copy operation greatly reduce the I/O subsystem throughput for database

operations, where transactions andfull-table scanoperations operatemorequickly with

no operating system data intervention.

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Red Hat APPLICATION STACK 1.1 RELEASE Bedienungsanleitung Seite 11