Re: [naviserver-devel] naviserver with connection thread queue

[Stephen D. <sd...@gm...>]

On Thu, Nov 29, 2012 at 6:51 PM, Gustaf Neumann <ne...@wu...> wrote:
>
> It turned out
> that the large queueing time came from requests from taipeh, which contained
> several 404 errors. The size of the 404 request is 727 bytes, and therefore
> under the writersize, which was configured as 1000. The delivery of an error
> message takes to this site more than a second. Funny enough, the delivery of
> the error message blocked the connection thread longer than the delivery of
> the image when it is above the writersize.
>
> I will reduce the writersize further, but still a slow delivery can even
> slow down the delivery of the headers, which happens still in the connection
> thread.

This shouldn't be the case for strings, or data sent from the fast
path cache, such as a small file (a custom 404), as eventually those
should work their way down to Ns_ConnWriteData which will construct
the headers if not already sent and pass them, along with the data
payload to writev(2). Linux should coalesce the buffers and send in a
single packet, if small enough.

I wonder if this is some kind of weird nsssl interaction.

(For things like sendfile without ssl we could use TCP_CORK to
coalesce the headers with the body)