Thanks for the response, Christian. I'll try doing some performance studies using an HTTP benchmark. So far, I've only looked at instruction counts for response processing, and noticed a significant reduction with qrintf. I'll take a look at whether there's a meaningful impact on overall performance.
Ariel ----- Original Message ----- From: groth...@gnunet.org To: libmicrohttpd@gnu.org, ariel.x.co...@oracle.com Sent: Wednesday, October 7, 2020 2:58:04 AM GMT -08:00 US/Canada Pacific Subject: Re: [libmicrohttpd] Improving response header build performance Hi Ariel, That's an interesting proposal, but I think it goes a bit into the wrong direction: - given that applications using MHD are likely to use printf() elsewhere, it'll almost certainly increase code size. I generally think for MHD code size is more important than speed. - given that the main application logic is virtually always going to be the bottleneck, I doubt this hyper-optimization will matter much in practice; so unless someone has a real-world application where they can show this matters, I think this is premature. - this change would increase code/build-system complexity, and likely hinder portability -- even if conditionally compiled. So without strong (performance) data on real (!) applications (not inet_ntop()) I would not seriously consider this. As the author of qrintf writes: this should be done by the compiler --- given the right compiler flags and iff the optimization is actually worth it. Happy hacking! Christian On 10/6/20 11:56 PM, Ariel Cohen wrote: > Hi, > > I noticed that adding response headers is expensive. One reason is that many > instructions are executed for the snprintf() calls which are invoked when > building response headers (build_header_response()). > > There is an sprintf accelerator called qrintf which rewrites invocations of > sprinf/snprintf to optimized forms. This is done by preprocessing the source > files using a filter program. See: > > https://github.com/h2o/qrintf > > This is provided under the MIT license, and I believe it is used in the H2O > HTTP server/library. > > Using this preprocessor on libmicrohttpd results in a significant reduction > in the instruction count for adding response headers during runtime. > > My question is whether this is something that could be considered for use by > libmicrohttpd in a future release. It would be helpful to improve the > performance of adding response headers. > > Thanks, > > Ariel >
