"query end" step very long at random times

Question

I'm benchmarking a web application, and I have a problem that occurs on about 1% of my queries, mostly UPDATES (but also sometimes INSERT). I did a profiling on those requests and it seems it's the query end step that takes a lot of time.

starting  0.000029
checking permissions  0.000005
Opening tables    0.000017
System lock   0.000005
init  0.000032
Updating  0.000052
end   0.000030
**query end   1.825892**
closing tables    0.000025
freeing items 0.000020
logging slow query    0.000007
logging slow query    0.000029
cleaning up   0.000008

As I went through the documentation

end : This occurs at the end but before the cleanup of ALTER TABLE, CREATE VIEW, DELETE, INSERT, SELECT, or UPDATE statements.

query end : This state occurs after processing a query but before the freeing items state.

So does this mean the cleanup of my UPDATE is taking time ? What does this step do exactly, how can I improve the performances ?

Thanks

Answer 1

Issue solved by adding

innodb_flush_log_at_trx_commit = 0

in the /etc/my.cnf

There is an interlocking problem when multiple threads want to write the file at the same time, this way the log will be flushed every second.