vms_iowait, vms_iowaitf Kernel Services

Purpose

Waits for the completion of all page-out operations for pages in the virtual memory object.

Syntax

#include <sys/types.h>
#include <sys/errno.h>
#include <sys/vmuser.h>

int vms_iowait ( vmid) vmid_t vmid;
int vms_iowaitf ( vmid, flags) vmid_t vmid; int flags;

Parameter

Item	Description
vmid	Identifies the virtual memory object for which to wait.
flags	Optional flags passed in by the user.

Description

The vms_iowait kernel service performs two tasks. First, it determines the I/O level at which all currently scheduled page-outs are complete for the virtual memory object specified by the vmid parameter. Then, the vms_iowait service places the current process in a wait state until this I/O level has been reached.

The I/O level value is a count of page-out operations kept for each virtual memory object.

The I/O level accounts for out-of-order processing by not incrementing the I/O level for new page-out requests until all previous requests are complete. Because of this, processes waiting on different I/O levels can be awakened after a single page-out operation completes.

If the caller holds the kernel lock, the vms_ iowait service releases the kernel lock before waiting and reacquires it afterwards.

The vms_iowait function is a special case of the vms_iowaitf function with the V_WAITERR flag set.

Flags

Name	Purpose
V_WAITERR	Waits until the completion of all I/O unless an error occurs.
V_WAITALL	Waits until the completion of all I/O regardless of any occurrence of I/O errors.

Execution Environment

The vms_iowait and vms_iowaitf kernel services can be called from the process environment only.

They can only be used by file segments.

Return Values

Item	Description
0	Indicates that the page-out operations completed.
EIO	Indicates that an error occurred while performing I/O.