Patch Name: PHKL_22310

Patch Description: s700 10.20 VxFS I/O throttling for slow devices

Creation Date: 00/09/12

Post Date:  00/09/22

Warning: 01/12/20 - This Non-Critical Warning has been issued by HP.

	- PHKL_22310 introduced behavior that can cause commands that
	  utilize the sync(2) system call to temporarily hang while
	  the system is copying VxFS file system information to disk.
	  The behavior can affect commands such as sync(1M), bdf(1M),
	  and login(1).  The most noticeable symptom reported thus far
	  has been exceedingly long delays, up to several minutes,
	  during user logins.
	- This behavior occurs when there is heavy activity on the
	  disk.  PHKL_22310 introduced a "throttling mechanism" to
	  improve performance to slower devices.  Unfortunately, under
	  heavy I/O this mechanism causes sync(2) to intermittently
	  wait for the disk to process I/O requests, resulting in
	  extended delays.
	- To avoid this behavior, HP recommends PHKL_22310 be removed
	  from all systems with VxFS file systems experiencing extended
	  delays during the login process, or when commands such as
	  sync(1M) or bdf(1M) are executed.
	- PHKL_22310 is included in the following Support Plus Patch
	  Bundles:
		Mar 2001: XSW700GR1020,B.10.20.52.2
		Jun 2001: XSW700GR1020,B.10.20.53.2
		Sep 2001: XSW700GR1020,B.10.20.54.1
		Dec 2001: XSW700GR1020,B.10.20.55.3

Hardware Platforms - OS Releases:
	s700: 10.20

Products: N/A

Filesets:
	JournalFS.VXFS-BASE-KRN

Automatic Reboot?: Yes

Status: General Release With Warnings

Critical: No

Path Name: /hp-ux_patches/s700/10.X/PHKL_22310

Symptoms:
	PHKL_22310:
	(SR: 8606157903   CR: JAGad27233)
	Systems with heavy I/O to slow devices may sometimes
	experience slow response time for processes trying to
	access the respective device.

Defect Description:
	PHKL_22310:
	(SR: 8606157903   CR: JAGad27233)
	The method used by VxFS filesystems for writing sequential
	data is to asynchronously write data up to a limit and when
	that limit is met, to delay-write the remaining data.  This
	data is flushed periodically.  The adverse effect of having
	a large amount of delayed-write data in the buffer cache is
	that it can potentially flood the device with requests.

	Resolution:
	In order to slow the amount of I/O requests made to
	devices that cannot keep up with demand a throttling
	mechanism will be put in place for flushes from the
	buffer cache to VxFS files that will prevent a device
	from being overloaded.

SR:
	8606157903

Patch Files:
	/usr/conf/lib/libvxfs_base.a(vx_chain.o)

what(1) Output:
	/usr/conf/lib/libvxfs_base.a(vx_chain.o):
		vx_chain.c $Date: 2000/09/11 14:58:05 $ $Revision: 1
			.7.98.7 $ PATCH_10.20 (PHKL_22310)

cksum(1) Output:
	3493577775 5492 /usr/conf/lib/libvxfs_base.a(vx_chain.o)

Patch Conflicts: None

Patch Dependencies:
	s700: 10.20: PHKL_16750

Hardware Dependencies: None

Other Dependencies: None

Supersedes: None

Equivalent Patches:
	PHKL_22311:
	s800: 10.20

Patch Package Size: 60 KBytes

Installation Instructions:
	Please review all instructions and the Hewlett-Packard
	SupportLine User Guide or your Hewlett-Packard support terms
	and conditions for precautions, scope of license,
	restrictions, and, limitation of liability and warranties,
	before installing this patch.
	------------------------------------------------------------
	1. Back up your system before installing a patch.

	2. Login as root.

	3. Copy the patch to the /tmp directory.

	4. Move to the /tmp directory and unshar the patch:

		cd /tmp
		sh PHKL_22310

	5a. For a standalone system, run swinstall to install the
	    patch:

		swinstall -x autoreboot=true -x match_target=true \
			-s /tmp/PHKL_22310.depot

	By default swinstall will archive the original software in
	/var/adm/sw/patch/PHKL_22310.  If you do not wish to retain a
	copy of the original software, you can create an empty file
	named /var/adm/sw/patch/PATCH_NOSAVE.

	WARNING: If this file exists when a patch is installed, the
	         patch cannot be deinstalled.  Please be careful
		 when using this feature.

	It is recommended that you move the PHKL_22310.text file to
	/var/adm/sw/patch for future reference.

	To put this patch on a magnetic tape and install from the
	tape drive, use the command:

		dd if=/tmp/PHKL_22310.depot of=/dev/rmt/0m bs=2k

Special Installation Instructions:
	This patch depends on base patch PHKL_16750 .
	For successful installation, please ensure that PHKL_16750
	is in the same depot with this patch, or PHKL_16750  is
	already installed.