[erlang-questions] performance issue with cowboy

[Loïc Hoguin]

Sure but everything you do through file:* goes through a single Erlang 
process except if you use the 'raw' option.

On 11/09/2014 04:37 PM, Shayan Pooya wrote:
> Hey Danil,
>
> Thanks for the response. Everything is buffered in the kernel-space
> anyway and there is no use for a user-space buffer in this case.
>
> On Sat, Nov 8, 2014 at 5:44 PM, Danil Zagoskin <z@REDACTED
> <mailto:z@REDACTED>> wrote:
>
>     Hi!
>
>     Did you do any profiling?
>
>     Reading the patch I noticed that you have replaced single
>     [Mochiweb's Req:stream_body + file:write] with
>     iterative [cowboy_req:body + file:write]. So your process now writes
>     to file (possibly blocking on it) every MTU (typically 1.5K) bytes
>     instead of single write — about 70K syscalls per second on gigabit
>     network.
>     I'd suggest adding a large buffer (e.g. 1 MB) to not access the file
>     too often.
>
>
>     On Sun, Nov 9, 2014 at 12:41 AM, Shayan Pooya <shayan@REDACTED
>     <mailto:shayan@REDACTED>> wrote:
>
>         Hello,
>
>         I have ported Disco to use cowboy instead of mochiweb. Mochiweb
>         has been quite stable and we did not have any issues with it
>         recently. However, cowboy uses the sendfile syscall which avoids
>         a lot of overhead when serving static files and I thought that
>         could lower the memory footprint of Disco when serving large
>         files and free up some cycles. Disco+cowboy is now fully
>         functional and all of the integration tests pass (minus some
>         minor missing features).
>
>         I wanted to get a sense of the performance before making the
>         switch and used a couple of different Disco jobs (which pressure
>         the web-servers) to do a comparison and the Disco version with
>         cowboy consistently takes 10 to 20 percent longer to finish. I
>         haven't done much for optimizing the usage of cowboy yet, but
>         the micro-benchmarks that I find on the web are contrary to what
>         I am seeing here and I wanted to know if anyone can offer some
>         guidance for getting better results with cowboy.
>
>         I am using cowboy 1.0.1 and the Cowboy patch for Disco is
>         available at https://github.com/pooya/disco/commit/5499d696438
>         just in case.
>
>         Regards.
>
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>
>
>
>     --
>     Danil Zagoskin | z@REDACTED <mailto:z@REDACTED>
>
>
>
>
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-- 
Loïc Hoguin
http://ninenines.eu