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

from [Rob Shepherd] [Permanent Link][Original]
To: Pasi Kärkkäinen <pasik@xxxxxx>
Subject: Re: [Xen-users] Java JVM and memory on Xen
From: Rob Shepherd <rs@xxxxxxxxxxxxx>
Date: Fri, 13 Nov 2009 21:58:13 +0000
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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 is stable when mem-set has been called with 1791 MB
This happens running JBoss, and is an actual libjvm.so Segfault. It doesn'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 any comments about why it may be happening?
One thought.... Java requires contiguous memory which I believe Xen does not provide to the guest. I would have thought however that the addressable memory space that an application 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 kernel boot 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 booted with 1791 and 1792 MB respectively.
I see no non-linear or unrealistic changes in the scenario. What do you think?
Also, this was taken on a debian kernel (2.6.26-2-xen-amd64) which bears the 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 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 



--
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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