Hi Joseph.
On 1 Apr 2007, at 14:03, Joseph Benden wrote:
> I'm trying to squeeze all the performance possible from every piece
> of my Solaris systems. The last piece that is bugging me is the
> high number of system calls experienced on the machines. In
> analyzing the web server, I found the problem was the read() system
> call. Next, I wanted to know what sizes were being read and where
> from. It turns out the read()s are from the mysqlclient library
> and are 4 byte reads.
>
> value ------------- Distribution ------------- count
> 0 | 0
> 1 |@@@@@ 3447
> 2 |@ 616
> 4 |@@@@@@@@@@@@@@@@@@@ 12531
> 8 |@ 626
> 16 |@@@@@@@@ 4966
> 32 |@@ 1158
> 64 | 153
> 128 | 29
> 256 | 15
> 512 | 5
> 1024 | 17
> 2048 | 0
> 4096 | 0
> 8192 |@@@@ 2667
> 16384 | 0
>
>
> Upon further research with dtrace, I've found these read()s to
> correspond with the MySQL protocol packet header being read().
>
> I was wondering why a buffered approach wasn't taken. ie: A
> general buffered read() of everything possible from the wire and
> the protocol code asking for the number of bytes from that buffered
> area. I feel that in doing this many system calls could be reduced,
> which would increase the speed of using the library.
While we are more sensitive to excessive syscalls since Bug#22943, we
still have room for improvement. The "vio" interface that we use for
(nearly) all I/O is nicely modular, but does need some attention, and
a buffer sounds like an excellent project that shouldn't take very
long and is rather cool. This would have wide-reaching effects, all
the way into the server; this is not a client-only problem.
Joseph, with your research so far, you are probably in a great
position to create heuristically good read() buffer sizes. Do you
feel comfortable taking on such a project?
If not, I'm sure someone else on this list would gladly take it.
In any case, this should be entered into our bug-tracking system. Do
you mind adding it, Joseph, along with any more detailed output from
your tracing tool?
- chad
--
Chad Miller, Software Developer chad@stripped
MySQL Inc., www.mysql.com
Orlando, Florida, USA 13-20z, UTC-0400
Office: +1 408 213 6740 sip:6740@stripped
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