Red Hat APPLICATION STACK 1.1 RELEASE Manuale Utente Scaricare il pdf (Pagina 13)

Feature Overview

Large Physical Memory Support

Large amounts of physical memory coupled with the ability to create large

(multi-gigabyte) shared memory segments provide a boost in performance to database

workloads.With this release,SGIhasincluded a conﬁguration parameter thatallowsthe

kernel to support more than 2 GB of physical memory (to approximately 3.8 GB) while

still providing a 3 GB application virtual (user) address space.

See “Changing Linux Kernels” on page 17 for information about building a kernel that

uses this feature.

Fast Synchronization Mechanism

WhiletheUNIXSystemV IPCsemaphorefacilitydoesprovideexceptional capability,its

performance leaves much to be desired. Many Unix vendors have released a

low-overhead inter-application synchronization primitive known as “post /wait.”

SGI has included in this release a kernel level implementation of post/wait along with

the library containing application API’s. The post allows for a process to “wait” for an

event. This event can either be a timeout or a “post” from another process. A group of

cooperating processes can use these “post” and “wait” facilities to synchronize among

themselves.

In order to use post/wait, the kernel must be compiled with the CONFIG_PW

conﬁguration variable, andyou may optionallyset an additionalconﬁguration variable,

CONFIG_PW_VMAX. These variables are described in the conﬁguration help. For a

user program to use the post/wait facilities, it must link against libdba.so.

For more information on post/wait, please refer to the postwait(3) man page.

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Red Hat APPLICATION STACK 1.1 RELEASE Manuale Utente Pagina 13