I had several ISO images lying around on my desktop, and decided to go through each image and purge the ones I no longer need. Several image files weren’t labeled, so I decided to fire up the isoinfo utility to figure out what the mystery ISO images were. The first image I checked was a Solaris 10 update 4 DVD, as you can see from the “Volume id” field in the isoinfo “-d” (print primary volume descriptor) output:
$ isoinfo -d -i 1.iso |more
CD-ROM is in ISO 9660 format
System id: Solaris
Volume id: SOL_10_807_X86
Volume set id:
Publisher id:
Data preparer id:
Application id: MKISOFS ISO 9660/HFS FILESYSTEM BUILDER & CDRECORD CD-R/DVD CRE
ATOR (C) 1993 E.YOUNGDALE (C) 1997 J.PEARSON/J.SCHILLING
Copyright File id:
Abstract File id:
Bibliographic File id:
Volume set size is: 1
Volume set sequence number is: 1
Logical block size is: 2048
Volume size is: 1327235
El Torito VD version 1 found, boot catalog is in sector 42171
NO Joliet present
Rock Ridge signatures version 1 found
Eltorito validation header:
Hid 1
Arch 0 (x86)
ID ''
Key 55 AA
Eltorito defaultboot header:
Bootid 88 (bootable)
Boot media 0 (No Emulation Boot)
Load segment 0
Sys type 0
Nsect 4
Bootoff A4BC 42172
To double check that the volume descriptor was correct, I also ran isoinfo with the “-l” (list files) option to generate a file listing of each ISO image:
$ isoinfo -l -i 1.iso |more
Directory listing of /
d--------- 0 0 0 4096 Aug 16 2007 [ 632 02] .
d--------- 0 0 0 4096 Aug 16 2007 [ 632 02] ..
---------- 0 0 0 2048 Aug 16 2007 [ 42171 00] .CATALOG
---------- 0 0 0 92 Jun 12 2007 [ 42231 00] .CDTOC
d--------- 0 0 0 2048 Aug 16 2007 [ 42045 02] .INSTALL
---------- 0 0 0 0 Aug 16 2007 [ 42173 00] .INSTALL_CONFIG
---------- 0 0 0 419 Jun 12 2007 [ 42232 00] .SLICEMAPFILE
d--------- 0 0 0 2048 Aug 16 2007 [ 42041 02] BOOT
---------- 0 0 0 6128 Jun 12 2007 [ 42233 00] COPYRIGHT
---------- 0 0 0 257 Aug 16 2007 [ 42236 00] INSTALLER
---------- 0 0 0 459760 Jun 12 2007 [ 42237 00] JDS-THIRDPARTYLICENSEREADME
d--------- 0 0 0 2048 Aug 16 2007 [ 634 02] LICENSE
d--------- 0 0 0 2048 Aug 16 2007 [ 635 02] SOLARIS_10
---------- 0 0 0 19 Jun 12 2007 [ 42462 00] _VOLUME.INF
---------- 0 0 0 21 Aug 16 2007 [ 42463 00] _VOLUME_INF.2
---------- 0 0 0 21 Aug 16 2007 [ 42464 00] _VOLUME_INF.3
---------- 0 0 0 21 Aug 16 2007 [ 42465 00] _VOLUME_INF.4
---------- 0 0 0 21 Aug 16 2007 [ 42466 00] _VOLUME_INF.5
With this information in hand, I added useful labels to the mystery images. Nice!
Roughly ten years ago one of my friends loaned me his copy of the Alice In Chain’s MTV unplugged CD. Since that time, I’ve listened to that CD thousands of times, and have become one of the biggest Alice In Chains fans on the planet. I have had the opportunity to see Jerry Cantrell play a number of shows across the country, and attended an Alice In Chains show earlier this year. During that show, the guys from AIC played an awesome acoustic set, which left me wanting more. A few months back I got notified that AIC was doing a number of acoustic shows across the country, so I decided to head down to New Orleans to check one out.
New Orleans is an incredible town, so I decided to wander down a couple of days early to relax and have a little fun. While relaxing on the top of the Omni hotel the night before the show, I looked over at the bar and saw Mike Inez (the Alice In Chain’s bassist) drinking it up with his friends. I was completely taken by this, and couldn’t believe that a member of one of my favorite bands was sitting twenty feet away from me. When Mike got up to leave, I stopped him for a second to tell him we ventured down to see him, and thanked him for putting on the acoustic show (I totally respect peoples privacy, so I kept the conversation to two sentences). He smiled, thanked us for coming, and then headed out to have some fun with his friends.
On the day of the show, I was still flying high from meeting one of the band members (I saw Jerry Cantrell in the hotel bar, but he was less than friendly for some reason), so I was hoping the acoustic show would elevate things to the next level. The band took the stage around 9:30pm, and opened the show with the song “Don’t Follow.” The sound system at the House of Blues really made the acoustic instruments stand out, and the opening song sounded absolutely incredible! Jerry, William, Mike and Sean followed up the opening song with a slew of classic AIC songs, including “Heaven Beside You,” “Brother,” “Nutshell,” “Killer is Me,” “Sludge Factory,” “Love Hate Love,” “No Excuses,” “Down in a Hole,” “Angry Chair,” “Got me Wrong,” “Would?” and “Rooster.” This show has to go down as one of the best concerts I have ever attended, and hearing these guys play acoustic made my year! Viva la AIC!!!
Java has become one of the most successful languages to hit the IT industry. One of the reasons behind it’s high rate of adoption is that fact that Java manages memory resources for the programmer. This makes programming significantly easier, but introduces additional complexity, since engineers need to size the Java heap and pick a garbage collection algorithm (or in the case of generational collectors, more than one) that best matches an application’s workload. Fortunately, two extremely useful tools allow you to observe the Java heap: the DTrace hotspot provider and the Java jmap utility. In this blog post, I will discuss the jmap utility.
The Java jmap utility provides a number of useful options to summarize heap usage, and get a break down of objects in the new and old generations. To summarize the new and old generations, the jmap utility can be run with the “-heap” option, and the PID of the JVM to summarize (the PID can be acquired by running the jps utility, or by reviewing the ps output):
$ jmap -heappgrep java``
Attaching to process ID 5365, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 1.6.0_01-b06
using parallel threads in the new generation.
using thread-local object allocation.
Concurrent Mark-Sweep GC
Heap Configuration:
MinHeapFreeRatio = 40
MaxHeapFreeRatio = 70
MaxHeapSize = 1073741824 (1024.0MB)
NewSize = 268435456 (256.0MB)
MaxNewSize = 268435456 (256.0MB)
OldSize = 805306368 (768.0MB)
NewRatio = 7
SurvivorRatio = 6
PermSize = 21757952 (20.75MB)
MaxPermSize = 88080384 (84.0MB)
Heap Usage:
New Generation (Eden + 1 Survivor Space):
capacity = 234881024 (224.0MB)
used = 102062424 (97.33431243896484MB)
free = 132818600 (126.66568756103516MB)
43.452818053109304% used
Eden Space:
capacity = 201326592 (192.0MB)
used = 94318424 (89.94905853271484MB)
free = 107008168 (102.05094146728516MB)
46.84846798578898% used
From Space:
capacity = 33554432 (32.0MB)
used = 7744000 (7.38525390625MB)
free = 25810432 (24.61474609375MB)
23.07891845703125% used
To Space:
capacity = 33554432 (32.0MB)
used = 0 (0.0MB)
free = 33554432 (32.0MB)
0.0% used
concurrent mark-sweep generation:
capacity = 805306368 (768.0MB)
used = 15032688 (14.336288452148438MB)
free = 790273680 (753.6637115478516MB)
1.8667042255401611% used
Perm Generation:
capacity = 50577408 (48.234375MB)
used = 30285240 (28.88225555419922MB)
free = 20292168 (19.35211944580078MB)
59.87898786746842% used
The jmap output contains the size of eden (the place where new objects are created), each survivor space, the old generation and the permanent generation. If you aren’t familiar with the generations that are used in modern JVMs, you might want to take a look at Tony Printezis’ article on this topic.
In addition to printing summary data, jmap can also be used to display the objects in the heap.
$ jmap -histopgrep java |more
num #instances #bytes class name
--------------------------------------
1: 224437 27673848 [C
2: 38611 23115312 [B
3: 47801 12187536 [I
4: 208624 8344960 java.lang.String
5: 45332 6192904 <constMethodKlass>
6: 45332 5450864 <methodKlass>
7: 3889 4615536 <constantPoolKlass>
8: 45671 4193136 [Ljava.lang.Object;
9: 66203 3222312 <symbolKlass>
10: 3889 3192264 <instanceKlassKlass>
11: 3455 2999296 <constantPoolCacheKlass>
12: 19754 1106224 java.nio.HeapCharBuffer
< ..... >
This summary contains the type of each object (e.g., “[C” would refer to arrays of characters), the number of objects of each type as well as the total number of bytes these objects take up in the heap. Jmap additionally allows you to filter the output to display only the live objects:
$ jmap -histo:live 698
num #instances #bytes class name
--------------------------------------
1: 45256 6185464
2: 45256 5441744
3: 6899 5201176 [B
4: 3851 4577776
5: 29133 4259592 [C
6: 66069 3213448
7: 3851 3169464
8: 3417 2970112
9: 29714 1188560 java.lang.String
10: 1553 745224
11: 4161 732336 java.lang.Class
< ..... >
There are also jmap options to dump the heap to a file, display the contents of the permanent generation and view obejcts that are awaiting finalization. Jmap is an incredibly useful tool, and in my next blog post I will show how the DTrace hotspot provider can be used to dig into object allocation in much more detail.
I came across the sdparm utility while surfing the web last weekend. This super useful utility can be used to display and modify SCSI device parameters, and is the best tool I’ve found for dumping SCSI mode and VPD pages. I wish sdparm would have been around when I was reading through the SBC documentation on the T11 website. That would have been swell!
In Solaris 10 the ptools (process tools) were enhanced to display data for specific threads in a process. This functionality can be tapped into by appending a slash and a thread id to the ptool command line:
$ pstack 739/2
739: java TestApp
----------------- lwp# 2 / thread# 2 --------------------
feeb3025 lwp_cond_wait (806eeb8, 806eea0, 0, 0)
feac58c1 __1cHMonitorEwait6Mbl_b_ (806ee48, 0, 0) + 2c1
feb28310 __1cHThreadsKdestroy_vm6F_b_ (0, 0, 806a79c, 0, 10006, febb59c9) + 7c
fe8e2de2 jni_DestroyJavaVM (fec46dc0) + 12a
0805324c JavaMain (8047cb8) + fec
feeae662 _thr_setup (fe650200) + 52
feeae8c0 _lwp_start (fe650200, 0, 0, 0, 0, 0)
This is extremely useful when you need to interrogate a specific thread in a process (e.g., a thread that is consuming 100% of a CPU), or when a process has 100s or 1000s of threads (which is typically the case with Java applications). Nice!