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тАО03-09-2009 08:24 AM
тАО03-09-2009 08:24 AM
Java performance issue on large directories
I am using SVNKIT (Java Subversion Client) on VMS Itanum V8.3. I have noticed that performance declines rapidly when checking out a large number of files to the _one_ directory .
Checking out 2700 files to one directory took close to an hour. When splitting the files into 7 subdirectories the execution time dropped from one hour to 10 minutes.
Has anyone noticed this? Anyone knows what to do about it? I have done the usual stuff, installed Java sharables resident, using pure ODS5 etc but it doesn't really help.
Any input or suggestion i s most welcome.
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тАО03-09-2009 09:18 AM
тАО03-09-2009 09:18 AM
Re: Java performance issue on large directories
10 minutes still sounds like 'for-ever'.
How long is the average file name?
Can you do something about order?
OpenVMS Directories 'like' two modes of acces.
1) add to end, and delete from end
2) removes and inserts ROUGHLY in the same sort order.
You may want to MEASURE what the system is doign during those 10 minutes (or that hour)
using $MONI FCP,FILE
Bettter still, have T4 do the collection and replay.
You may need to ADJUST the SYSGEN ACP params for this application.
Notably: $MCR SYSGEN SHOW /ACP
ACP_MAXREAD
ACP_DIRCACHE
Hope this helps some,
Hein van den Heuvel ( at gmail dot com )
HvdH Performance COnsulting
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тАО03-10-2009 10:21 AM
тАО03-10-2009 10:21 AM
Re: Java performance issue on large directories
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тАО03-27-2009 06:48 AM
тАО03-27-2009 06:48 AM
Re: Java performance issue on large directories
I am posting this for the benefit of other OpenVMS SVNKIT users.
I have had problems checking out/updating large directories, 2700 files or more. The check out time was 60 (sixty) minutes and the CPU time just as much.
After defining svnkit.symlinks=false the checkout time dropped from 60 minutes to 4 minutes.
I added the following change to startup file "jsvnsetup.openvms".
It is important that the quoting is exactly as below to get the final jsvn command right.
....
$ OPT = """""-Dsvnkit.symlinks=false"""""
......
Anders Wallin
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тАО03-27-2009 12:22 PM
тАО03-27-2009 12:22 PM
Re: Java performance issue on large directories
Excellent feedback.
Of course it begets the question what it all does extra when symlinks are enabled. Might be a porting problem? Did it matter whether the directory was on an ODS-2 or ODS-5 structure level disk, or is ODS-5 requiered per chance?!
Anyway.. thanks!
Hein.
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тАО03-29-2009 12:56 PM
тАО03-29-2009 12:56 PM
Re: Java performance issue on large directories
What is the size of the directory file itself, and does the operation involve deleting files (or directory entries)?
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тАО03-29-2009 02:19 PM
тАО03-29-2009 02:19 PM
Re: Java performance issue on large directories
http://www.nabble.com/Re%3A-svnkit-cli-slow-on-large-dirs-%28many-files%29-p12255769.html
Basically the JDK does not have a way to check whether a file is a symlink, so they do some evil hack to figure it out. What it *sounds* like they are doing is spawning an ls command and rooting through the output. I think the polite thing to call such an approach is "architecturally challenged."
In C you would just call lstat() and check the st_mode field with the S_ISLNK macro. Seems like a few lines of JNI code would do the trick, though then they'd have platform-specific bits to maintain and distribute.
Turning off symlink support does seem like the right thing to do here.
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тАО03-29-2009 10:03 PM
тАО03-29-2009 10:03 PM
Re: Java performance issue on large directories
>In C you would just call lstat
On HP-UX, I see calls to readlink(2).