I couldn't find an appropriate ticket, so opening this new one.
While this is not really a bug, its about how Devel disinforms users on database operations performance.
Devel shows query statistics making a user to think that this is probably all what was happening to DB when a page have being built. But apart from queries there are commits, which are not counted but which could be more time consuming in 10 and 20 times then "queries", depending on DB and host configuration.

To see what consequences this reduction could lead to read this post: http://drupal.org/node/1661608
In short, a Devel query statistics where inaccurate in 10-20 times!

Example: on Core i7/16Gb desktop, a page was loading for 16 seconds (after cache cleaning), and Devel query counters was displaying 800ms, while real time consumed by DB layer was about 15000ms.

Conclusion

Either commits stats should be counted too, or a red bold warning should be added to the Devel configuration page saying that the real database workload could differ in any amount of times than is shown by the counter.

CommentFileSizeAuthor
#1 XHProf.jpg290.93 KBmilesw
#1 Devel.jpg268.75 KBmilesw
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OnkelTem’s picture

Issue summary: View changes

asd

milesw’s picture

Issue summary: View changes
FileSize
268.75 KB
290.93 KB

I'm noticing this as well and hoping someone more knowledgable can help explain.

Here is the Devel query log and the XHProf run for the same page request:

The query count from Devel and call count from XHProf correspond pretty closely. So do the total query time from Devel and self wall time from XHProf.

But the CPU time recorded by XHProf suggests there's a lot more happening with the database.

Is the discrepancy due to commits, as the OP suggests? What else might account for the additional time?

willzyx’s picture

Status: Active » Closed (outdated)

Closing for lack of activity. Feel free to reopen if the issue still exists