On Thu, 9 Jul 2020 at 18:01, Aniruddh Agarwal via Boost-users < boost-users@lists.boost.org> wrote:
> On Jul 9, 2020, at 10:49 AM, Richard Hodges via Boost-users < > boost-users@lists.boost.org> wrote: > > It's not equivalent because in the case of one thread per io_context, > the completion handler of asynchronous operations will always be invoked on > a known thread. Therefore concurrency protection is not a concern. > > > > If you use the executor of a thread_pool, there is no guarantee which > thread will invoke the completion handler, and no guarantee that two > completion handlers will not touch the same user object. This argues for > the use of asio::strand<asio::thread_pool::executor_type> as the executor > to be associated with the completion handler (or set as the default > executor of related io objects). > > It seems that my original email was a bit misleading and implied that I > was comparing (many threads, many asio::io_context objects) with > asio::thread_pool. In fact, I’m trying to compare (many threads, one > asio::io_context object) with asio::thread_pool. From what you’ve said > above, it looks like (many threads, one asio::io_context object) and > asio::thread_pool are logically equivalent. > >From the soon to be released boost 1.74 docs, the executor_type of io_context and thread_pool are the same type: typedef basic_executor_type< std::allocator< void >, 0 > executor_type; , so it seems that it is intended that they will have the same behaviour. > > Can you speak to any performance differences between these (or point to > reference material which touches on this)? > I cannot point you to material offhand, but you have reminded me that I read this *somewhere*. I seem to remember something about there needing to be something that's calling epoll/select/pselect in a loop. But now you've got me wondering if I am mistaken. Of course if your worker thread is just making a blocking call to run(), that's where the io loop will happen. Your handlers will be executed within the context of the io_context::run which will happen on a thread associated with the thread_pool. > > Is there a use case or is this a question out of curiosity? > > Mostly out of curiosity. I’ve found myself repeatedly writing code where a > single asio::io_context is dishing out tasks to many threads, and am > wondering if asio::thread_pool is a drop-in replacement for manually > setting up a thread pool and calling asio::io_context::run from each thread. > I suppose this could save you a few lines of code. > > -Ani > > _______________________________________________ > Boost-users mailing list > Boost-users@lists.boost.org > https://lists.boost.org/mailman/listinfo.cgi/boost-users > -- Richard Hodges hodge...@gmail.com office: +442032898513 home: +376841522 mobile: +376380212
_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org https://lists.boost.org/mailman/listinfo.cgi/boost-users
