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Re: [Xen-users] Java JVM and memory on Xen

To: Pasi Kärkkäinen <pasik@xxxxxx>
From: Rob Shepherd <rs@xxxxxxxxxxxxx>
Date: Fri, 13 Nov 2009 21:58:13 +0000
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Delivery-date: Fri, 13 Nov 2009 13:59:31 -0800
List-id: Xen user discussion <xen-users.lists.xensource.com>

Pasi Kärkkäinen wrote:

On Tue, Nov 10, 2009 at 01:52:34PM +0000, Rob Shepherd wrote:
Hi,

I have a strange problem here.
My Java Virtual Machine crashes on a DomU when mem-set is 1792 MB but isstable when mem-set has been called with 1791 MB
This happens running JBoss, and is an actual libjvm.so Segfault. Itdoesn't report anything about memory etc.
Running:
very recent quad core Xeon 2Ghz,
Xen 3.1 from OpenSolaris 09/06
OpenSolaris 09/06 Dom0
Ubuntu 8.04 with 2.6.24-25-xen kernel image
JVMs (any... 1.5.0 - 1.7, either openjdk or sun)

I finally tracked down the crash to that single 1MB adjustment of RAM.

although the JVM is only configured to use 512MB of RAM MAX (-Xmx512m)
This is very bizarre. Has anybody seen behaviour before, or have anycomments about why it may be happening?
One thought.... Java requires contiguous memory which I believe Xen doesnot provide to the guest.I would have thought however that the addressable memory space that anapplication sees can be mapped to appear contiguous?
Thanks for any input, or suggestions
Does domU kernel dmesg have errors?

How does the domU kernel memory layout change when you switch between
1791 and 1792 MB of RAM? (it's in the beginning of dmesg / domU kernelboot messages).
Have you tried any other domU kernels? Ubuntu 2.6.24 kernel is known to
be buggy..

-- Pasi


Thank you for your input Pasi,

Below is a unified diff of the appropriate parts or kern.log when bootedwith 1791 and 1792 MB respectively.

I see no non-linear or unrealistic changes in the scenario. What do youthink?

Also, this was taken on a debian kernel (2.6.26-2-xen-amd64) which bearsthe same result as the ubuntu 2.6.24 kernel.


I am about to try a xen HVM image.

Any further input is greatly appreciated

A great many thanks

Rob

Here's the kern.log diff

--- kern.log-1791MB-a    2009-11-13 21:47:51.944593412 +0000
+++ kern.log-1792MB-a    2009-11-13 21:49:36.885698062 +0000
@@ -3,11 +3,11 @@
Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] Linux version2.6.26-2-xen-amd64 (Debian 2.6.26-20) (dannf@xxxxxxxxxx) (gcc version4.1.3 20080704 (prerelease) (Debian 4.1.2-25)) #1 SMP Mon Oct 2612:43:40 UTC 2009Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] Command line:root=UUID=1141efa3-ef46-4265-81b2-8b7c7332b26c ro console=hvc0 xencons=ttyNov 13 22:00:00 dev-perftest kernel: [ 0.000000] BIOS-providedphysical RAM map:-Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] Xen:0000000000000000 - 0000000070700000 (usable)-Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] Enteringadd_active_range(0, 0, 460544) 0 entries of 256 used-Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] max_pfn_mapped =460544+Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] Xen:0000000000000000 - 0000000070800000 (usable)+Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] Enteringadd_active_range(0, 0, 460800) 0 entries of 256 used+Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] max_pfn_mapped =460800
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000] init_memory_mapping
-Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] Enteringadd_active_range(0, 0, 460544) 0 entries of 256 used+Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] Enteringadd_active_range(0, 0, 460800) 0 entries of 256 usedNov 13 22:00:00 dev-perftest kernel: [ 0.000000] early res: 0[200000-631917] TEXT DATA BSSNov 13 22:00:00 dev-perftest kernel: [ 0.000000] early res: 1[632000-1cb4fff] Xen providedNov 13 22:00:00 dev-perftest kernel: [ 0.000000] early res: 2[1cb5000-1cb5fff] INITMAP
@@ -18,18 +18,18 @@
Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] Normal1048576 -> 1048576Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] Movable zonestart PFN for each nodeNov 13 22:00:00 dev-perftest kernel: [ 0.000000] early_node_map[1]active PFN ranges-Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] 0: 0-> 460544-Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] On node 0totalpages: 460544+Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] 0: 0-> 460800+Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] On node 0totalpages: 460800Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] DMA zone: 56pages used for memmapNov 13 22:00:00 dev-perftest kernel: [ 0.000000] DMA zone: 0pages reservedNov 13 22:00:00 dev-perftest kernel: [ 0.000000] DMA zone: 4040pages, LIFO batch:0-Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] DMA32 zone:6241 pages used for memmap-Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] DMA32 zone:450207 pages, LIFO batch:31+Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] DMA32 zone:6244 pages used for memmap+Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] DMA32 zone:450460 pages, LIFO batch:31Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] Normal zone: 0pages used for memmapNov 13 22:00:00 dev-perftest kernel: [ 0.000000] Movable zone: 0pages used for memmapNov 13 22:00:00 dev-perftest kernel: [ 0.000000] PERCPU:Allocating 22192 bytes of per cpu dataNov 13 22:00:00 dev-perftest kernel: [ 0.000000] NR_CPUS: 32,nr_cpu_ids: 4-Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] Built 1 zonelistsin Zone order, mobility grouping on. Total pages: 454247+Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] Built 1 zonelistsin Zone order, mobility grouping on. Total pages: 454500Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] Kernel commandline: root=UUID=1141efa3-ef46-4265-81b2-8b7c7332b26c ro console=hvc0xencons=tty
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000] Initializing CPU#0
Nov 13 22:00:00 dev-perftest kernel: [ 0.000000] PID hash tableentries: 4096 (order: 12, 32768 bytes)
@@ -39,5 +39,5 @@
Nov 13 22:00:00 dev-perftest kernel: [ 0.004000] Dentry cache hashtable entries: 262144 (order: 9, 2097152 bytes)Nov 13 22:00:00 dev-perftest kernel: [ 0.004000] Inode-cache hashtable entries: 131072 (order: 8, 1048576 bytes)Nov 13 22:00:00 dev-perftest kernel: [ 0.004000] Software IO TLBdisabled-Nov 13 22:00:00 dev-perftest kernel: [ 0.004000] Memory:1774016k/1842176k available (2279k kernel code, 59540k reserved, 1023kdata, 216k init)+Nov 13 22:00:00 dev-perftest kernel: [ 0.004000] Memory:1775040k/1843200k available (2279k kernel code, 59540k reserved, 1023kdata, 216k init)Nov 13 22:00:00 dev-perftest kernel: [ 0.004000] CPA: page poolinitialized 1 of 1 pages preallocated




--
Rob Shepherd BEng PhD - Director / Senior Engineer - DataCymru Ltd
Reg. England and Wales - 06731289 - TechniumCAST, LL57 4HJ
rs@xxxxxxxxxxxxx - 08452575006 - 07596154845 - www.datacymru.net

--- kern.log-1791MB-a   2009-11-13 21:47:51.944593412 +0000
+++ kern.log-1792MB-a   2009-11-13 21:49:36.885698062 +0000
@@ -3,11 +3,11 @@
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000] Linux version 
2.6.26-2-xen-amd64 (Debian 2.6.26-20) (dannf@xxxxxxxxxx) (gcc version 4.1.3 
20080704 (prerelease) (Debian 4.1.2-25)) #1 SMP Mon Oct 26 12:43:40 UTC 2009
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000] Command line: 
root=UUID=1141efa3-ef46-4265-81b2-8b7c7332b26c ro console=hvc0 xencons=tty
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000] BIOS-provided physical RAM 
map:
-Nov 13 22:00:00 dev-perftest kernel: [    0.000000]  Xen: 0000000000000000 - 
0000000070700000 (usable)
-Nov 13 22:00:00 dev-perftest kernel: [    0.000000] Entering 
add_active_range(0, 0, 460544) 0 entries of 256 used
-Nov 13 22:00:00 dev-perftest kernel: [    0.000000] max_pfn_mapped = 460544
+Nov 13 22:00:00 dev-perftest kernel: [    0.000000]  Xen: 0000000000000000 - 
0000000070800000 (usable)
+Nov 13 22:00:00 dev-perftest kernel: [    0.000000] Entering 
add_active_range(0, 0, 460800) 0 entries of 256 used
+Nov 13 22:00:00 dev-perftest kernel: [    0.000000] max_pfn_mapped = 460800
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000] init_memory_mapping
-Nov 13 22:00:00 dev-perftest kernel: [    0.000000] Entering 
add_active_range(0, 0, 460544) 0 entries of 256 used
+Nov 13 22:00:00 dev-perftest kernel: [    0.000000] Entering 
add_active_range(0, 0, 460800) 0 entries of 256 used
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000]   early res: 0 
[200000-631917] TEXT DATA BSS
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000]   early res: 1 
[632000-1cb4fff] Xen provided
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000]   early res: 2 
[1cb5000-1cb5fff] INITMAP
@@ -18,18 +18,18 @@
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000]   Normal    1048576 ->  
1048576
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000] Movable zone start PFN for 
each node
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000] early_node_map[1] active 
PFN ranges
-Nov 13 22:00:00 dev-perftest kernel: [    0.000000]     0:        0 ->   460544
-Nov 13 22:00:00 dev-perftest kernel: [    0.000000] On node 0 totalpages: 
460544
+Nov 13 22:00:00 dev-perftest kernel: [    0.000000]     0:        0 ->   460800
+Nov 13 22:00:00 dev-perftest kernel: [    0.000000] On node 0 totalpages: 
460800
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000]   DMA zone: 56 pages used 
for memmap
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000]   DMA zone: 0 pages 
reserved
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000]   DMA zone: 4040 pages, 
LIFO batch:0
-Nov 13 22:00:00 dev-perftest kernel: [    0.000000]   DMA32 zone: 6241 pages 
used for memmap
-Nov 13 22:00:00 dev-perftest kernel: [    0.000000]   DMA32 zone: 450207 
pages, LIFO batch:31
+Nov 13 22:00:00 dev-perftest kernel: [    0.000000]   DMA32 zone: 6244 pages 
used for memmap
+Nov 13 22:00:00 dev-perftest kernel: [    0.000000]   DMA32 zone: 450460 
pages, LIFO batch:31
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000]   Normal zone: 0 pages 
used for memmap
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000]   Movable zone: 0 pages 
used for memmap
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000] PERCPU: Allocating 22192 
bytes of per cpu data
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000] NR_CPUS: 32, nr_cpu_ids: 4
-Nov 13 22:00:00 dev-perftest kernel: [    0.000000] Built 1 zonelists in Zone 
order, mobility grouping on.  Total pages: 454247
+Nov 13 22:00:00 dev-perftest kernel: [    0.000000] Built 1 zonelists in Zone 
order, mobility grouping on.  Total pages: 454500
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000] Kernel command line: 
root=UUID=1141efa3-ef46-4265-81b2-8b7c7332b26c ro console=hvc0 xencons=tty
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000] Initializing CPU#0
 Nov 13 22:00:00 dev-perftest kernel: [    0.000000] PID hash table entries: 
4096 (order: 12, 32768 bytes)
@@ -39,5 +39,5 @@
 Nov 13 22:00:00 dev-perftest kernel: [    0.004000] Dentry cache hash table 
entries: 262144 (order: 9, 2097152 bytes)
 Nov 13 22:00:00 dev-perftest kernel: [    0.004000] Inode-cache hash table 
entries: 131072 (order: 8, 1048576 bytes)
 Nov 13 22:00:00 dev-perftest kernel: [    0.004000] Software IO TLB disabled
-Nov 13 22:00:00 dev-perftest kernel: [    0.004000] Memory: 1774016k/1842176k 
available (2279k kernel code, 59540k reserved, 1023k data, 216k init)
+Nov 13 22:00:00 dev-perftest kernel: [    0.004000] Memory: 1775040k/1843200k 
available (2279k kernel code, 59540k reserved, 1023k data, 216k init)
 Nov 13 22:00:00 dev-perftest kernel: [    0.004000] CPA: page pool initialized 
1 of 1 pages preallocated

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References:
- [Xen-users] Java JVM and memory on Xen
  - From: Rob Shepherd
- Re: [Xen-users] Java JVM and memory on Xen
  - From: Pasi Kärkkäinen

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