Hi John -
Good points, but we've long given up on MessageTally and replaced it with our own SystemProfiler and I do really trust its results. So the question still stands: Why could write() possibly be so slow?
Cheers, - Andreas
John M McIntosh wrote:
mmm I do need to ask how do you know the measurements are correct? Well assuming you used message tally?
I noticed in some benchmarking of object file out that it was saying 20% of the time in this case 24 SECONDS was taken up in SystemDictionary(IdentityDictionary)>>scanFor: in looking at why by adding a method to SystemDictionary and collecting information about the number of objects been looked for, and how many milliseconds I came to the conclusion that message tally was lying, there was only 90 some usages, accounting for 0 milliseconds.
However I've not been able to determine why it's broken. System (System-adrian_lienhard.ducasse.207) btw
In the past I've suggested using the message tracing VM and logging information in a more meaningful way since that hooks into the actual message send in the VM would give exact information. Plus it would leave less foot prints in the image since you aren't mixing another process (tally keeping) into the running of the smalltalk code.
On 17-Feb-09, at 6:38 PM, Andreas Raab wrote:
Folks -
I've been doing a bit of load-testing on our servers and thing that surprised me was that even in moderate load tests the VM appears to be spending some 20-30% of its total execution time in Socket>>primSocket:sendData:startIndex:count:. This is roughly at a throughput of 10Mbit so nothing spectacular and a long ways before we hit our bandwidth limits.
Given that the primitive in the Unix VM appears to be a vanilla call to write() I cannot possibly imagine what could cause this to take that much time. Also, all of these sends are guarded so socketSendDone: returned true prior to calling the send function (socketSendDone: takes about 2% total time in the profiles).
Has anyone seen similar behavior or has an idea on how to find out what is going on? If this is known write() behavior I would definitely consider putting this into a pthread for our servers. It is currently by far the biggest bottleneck that I can see.
Any ideas?
Cheers,
- Andreas
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John M. McIntosh johnmci@smalltalkconsulting.com Corporate Smalltalk Consulting Ltd. http://www.smalltalkconsulting.com ===========================================================================