Patch Name: PHKL_24974

Patch Description: s700_800 11.20 Page table spinlock deadlock, vm performance

Creation Date: 01/08/22

Post Date:  01/09/14

Hardware Platforms - OS Releases:
	s700: 11.20
	s800: 11.20

Products: N/A

Filesets:
	OS-Core.CORE2-KRN,fr=B.11.20,fa=HP-UX_B.11.20_64,v=HP

Automatic Reboot?: Yes

Status: General Release

Critical:
	Yes
	PHKL_24974: PANIC

Category Tags:
	defect_repair general_release critical panic

Path Name: /hp-ux_patches/s700_800/11.X/PHKL_24974

Symptoms:
	PHKL_24974:
	( SR:8606205066 CR:JAGad74242 )
	Poor scaling of applications that do numerous creations and
	deletions of virtual address translations may occur on
	systems with eight or more processors.

	( SR:8606206213 CR:JAGad75388 )
	System panics with a spinlock deadlock.  The stack trace
	looks similar to the following:

	Stack Trace:
	  IP                  Function Name
	  0xe0000000001fd450  too_much_time+0x3f0
	  0xe0000000001fcef0  wait_for_lock_ia+0x210
	  0xe000000000799e40  spinlock_errata_97+0x30
	  0xe0000000003e94b0  ptremap+0x160
	  ...

	"ptremap" may be "ptvpfn", "ptapage", "ptdpage", or another
	function name starting with "pt".

Defect Description:
	PHKL_24974:
	( SR:8606205066 CR:JAGad74242 )
	There is a single linked list of free (unused) page table
	entries for the system.  Only one processor at a time can be
	removing or returning an entry to this list.  This becomes a
	bottleneck if there is a lot of activity on the free list.

	Additionally, there are only 32 locks protecting the page
	table entries that are in use.  This can cause contention on
	an eight-way system or larger when each processor may be
	holding up to two locks.

	Resolution:
	Each processor now uses its own linked list of free
	page table entries and the number of locks for the
	page table entries in use was increased from 32 to
	4096.

	( SR:8606206213 CR:JAGad75388 )
	There is a hashed look-up table to convert virtual addresses
	to physical addresses.  The spinlock deadlock is a result of
	an entry in that table being linked to itself.  This results
	in an infinite loop when that table entry is accessed and
	the page table entry spinlock is held for too long.

	A page table entry can be linked to itself if the old and
	new virtual addresses from a physical page remapping, an
	operation done often by network and disk I/O drivers, have
	the same hash result.  This situation occurs because the
	remap functions add the page table entry to a hash chain
	that it is already on.

	Resolution:
	The functions which remap page translations now specifically
	check whether the hash values of the old and new virtual
	addresses are the same.  If they are the same, the functions
	do not attempt to add a page table entry to a hash chain
	that it is already on.

SR:
	8606205066 8606206213

Patch Files:
	
	OS-Core.CORE2-KRN,fr=B.11.20,fa=HP-UX_B.11.20_64,v=HP:
	/usr/conf/lib/libinit-pdk.a(sysinit.o)
	/usr/conf/lib/libshutdown-pdk.a(machdep.o)
	/usr/conf/lib/libtest-pdk.a(exer_md_os_mca.o)
	/usr/conf/lib/libtest-pdk.a(exer_md_pte.o)
	/usr/conf/lib/libvm-pdk.a(mem.o)
	/usr/conf/lib/libvm-pdk.a(vm_vhpt.o)

what(1) Output:
	
	OS-Core.CORE2-KRN,fr=B.11.20,fa=HP-UX_B.11.20_64,v=HP:
	/usr/conf/lib/libinit-pdk.a(sysinit.o):
		sysinit.c $Date: 2001/08/18 15:04:13 $Revision: r11.
			20/2 PATCH_11.20 (PHKL_24974)
	/usr/conf/lib/libshutdown-pdk.a(machdep.o):
		machdep.c $Date: 2001/08/18 15:04:13 $Revision: r11.
			20/1 PATCH_11.20 (PHKL_24974)
	/usr/conf/lib/libtest-pdk.a(exer_md_os_mca.o):
		exer_md_os_mca.c $Date: 2001/08/18 15:04:13 $Revisio
			n: r11.20/1 PATCH_11.20 (PHKL_24974)
	/usr/conf/lib/libtest-pdk.a(exer_md_pte.o):
		exer_md_pte.c $Date: 2001/08/18 15:04:13 $Revision: 
			r11.20/1 PATCH_11.20 (PHKL_24974)
	/usr/conf/lib/libvm-pdk.a(mem.o):
		mem.c $Date: 2001/08/18 15:04:13 $Revision: r11.20/1
			 PATCH_11.20 (PHKL_24974)
	/usr/conf/lib/libvm-pdk.a(vm_vhpt.o):
		vm_vhpt.c $Date: 2001/08/18 15:04:13 $Revision: r11.
			20/1 PATCH_11.20 (PHKL_24974)

cksum(1) Output:
	
	OS-Core.CORE2-KRN,fr=B.11.20,fa=HP-UX_B.11.20_64,v=HP:
	4035875051 25328 /usr/conf/lib/libinit-pdk.a(sysinit.o)
	3227144929 22000 /usr/conf/lib/libshutdown-pdk.a(machdep.o)
	1255851450 1344 /usr/conf/lib/
		libtest-pdk.a(exer_md_os_mca.o)
	3036369783 204344 /usr/conf/lib/libtest-pdk.a(exer_md_pte.o)
	1971195516 34256 /usr/conf/lib/libvm-pdk.a(mem.o)
	1754934641 220640 /usr/conf/lib/libvm-pdk.a(vm_vhpt.o)

Patch Conflicts: None

Patch Dependencies: None

Hardware Dependencies: None

Other Dependencies: None

Supersedes: None

Equivalent Patches: None

Patch Package Size: 520 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_24974

	5. Run swinstall to install the patch:

		swinstall -x autoreboot=true -x patch_match_target=true \
			  -s /tmp/PHKL_24974.depot

	By default swinstall will archive the original software in 
	/var/adm/sw/save/PHKL_24974.  If you do not wish to retain a
	copy of the original software, include the patch_save_files
	option in the swinstall command above:

		-x patch_save_files=false

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

	For future reference, the contents of the PHKL_24974.text file is 
	available in the product readme:

		swlist -l product -a readme -d @ /tmp/PHKL_24974.depot

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

		dd if=/tmp/PHKL_24974.depot of=/dev/rmt/0m bs=2k

Special Installation Instructions: None