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| LogBufferPages |
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| mattfarney |
 Posted: Fri Nov 18, 2011 1:39 pm Post subject: LogBufferPages |
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Disciple
Joined: 17 Jan 2006
Posts: 167
Location: Ohio
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Here's the text from the manual
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The amount of memory allocated to buffer records for writing, specifying the size of the buffers in units of 4 KB pages.
The minimum number of buffer pages is 18 and the maximum is 4096. Larger buffers lead to higher throughput, especially for larger messages.
If you specify 0 (the default), the queue manager selects the size. In WebSphere MQ Version 7.0 this is 512 (2048 KB).
If you specify a number between 1 and 17, the queue manager defaults to 18 (72 KB). If you specify a number between 18 and 4096, the queue manager uses the number specified to set the memory allocated. |
There are a couple of things in here that are vague to me.
Clearly, a larger buffer allows writes to happen faster, so the technique makes sense. I'm just trying to figure out how much I care.
In particular
| Quote: |
| Larger buffers lead to higher throughput, especially for larger messages |
begs the question, what is a "larger" message? 2k? 100k? 5Mb? Bigger?
Are there any white papers that explain how much faster things are when comparing say the default to the max?
The text didn't say so, but I'm assuming this is a run-time modifiable field. It didn't say whether or not a QM bounce was required or not.
-mf |
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| mvic |
| Posted: Fri Nov 18, 2011 1:49 pm Post subject: Re: LogBufferPages |
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Jedi
Joined: 09 Mar 2004
Posts: 2080
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LogBufferPages is a qm.ini parameter so the qm would need to be restarted, to see the change.
You can search the internet for LogBufferPages and get a bit more from ibm.com than you might have seen already.
And finally, no-one can tell you whether it will make much of a difference in your specific case. There are too many variables: message size, message persistence, concurrency of application usage, I/O latency and data rates, etc. etc. The only real way to know is to try changing the buffer size and measure the performance gain you get. |
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| PeterPotkay |
| Posted: Fri Nov 18, 2011 4:12 pm Post subject: |
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Poobah
Joined: 15 May 2001
Posts: 7722
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I never understood this one. Who wouldn't just set it to the highest value and be done with it? 4096 = 16 MB. You're telling me your server can't spare 16 MB of memory? Maybe in 1998 this was an issue, but in 2011?
_________________
Peter Potkay
Keep Calm and MQ On |
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| bruce2359 |
| Posted: Fri Nov 18, 2011 4:20 pm Post subject: |
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Poobah
Joined: 05 Jan 2008
Posts: 9471
Location: US: west coast, almost. Otherwise, enroute.
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LogBufferPages occupy virtual storage, which in turn occupy real storage (RAM). RAM is a finite resource.
If you have more RAM, allocating more LogBufferPages should improve throughput for this qmgr. Over-allocating RAM can be wasteful.
There are other configuration opportunities - some related to logging, others not related to logging.
What are your goals here? Is there a problem you are trying to address? Are you looking solely at tuning log buffers? Logging generally? Qmgr performance (throughput)) generally?
_________________
I like deadlines. I like to wave as they pass by.
ב''ה
Lex Orandi, Lex Credendi, Lex Vivendi. As we Worship, So we Believe, So we Live. |
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| mattfarney |
| Posted: Mon Nov 21, 2011 12:29 pm Post subject: |
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Disciple
Joined: 17 Jan 2006
Posts: 167
Location: Ohio
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To be honest, I'm trying to figure out if I care. There are always settings and configuration changes that can make things faster. I'm trying to decide if it's worth trying the higher settings on this (i.e. will I see a difference) versus the risk of change.
-mf |
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| zpat |
| Posted: Mon Nov 21, 2011 12:59 pm Post subject: |
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Jedi Council
Joined: 19 May 2001
Posts: 5866
Location: UK
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It makes some difference, but going to SingleWrite makes much more.
Now we will get everyone chipping in saying how this is dangerous.
Well it isn't on SAN storage with NVRAM, UPS etc, and is there anyone who doesn't use modern SAN storage these days? |
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| bruce2359 |
| Posted: Mon Nov 21, 2011 3:05 pm Post subject: |
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Poobah
Joined: 05 Jan 2008
Posts: 9471
Location: US: west coast, almost. Otherwise, enroute.
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| mattfarney wrote: |
| To be honest, I'm trying to figure out if I care. |
That's the spirit! 
_________________
I like deadlines. I like to wave as they pass by.
ב''ה
Lex Orandi, Lex Credendi, Lex Vivendi. As we Worship, So we Believe, So we Live. |
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