Re: [Boost-users] synchronous vs asynchronous...

Subject: Re: [Boost-users] synchronous vs asynchronous...
From: Oliver Seiler (oseiler_at_[hidden])
Date: 2009-07-23 17:57:21

Unfortunately threads on most OSs are as much a resource as memory.
Using them as if they are "cheap" is typically a recipe for poor
performance. Read some of Herb Sutter's recent articles on DDJ Online
on using threads effectively, especially on multicore CPUs. Have a
look at Intel's Threading Building Blocks library.

In POSIX-land (where I live) at the simplest, I would dedicate a
thread to all socket I/O (via select, poll, epoll, pick your poison);
running a thread per connection scales poorly (not to mention would
limit the number of concurrent connections, depending on your OS --
definitely under Linux). Typically you'd dispatch the work to another
pool of threads. Anything that will block for a while I'd like to
isolate to a thread, keeping CPU-bound work to a fixed-size thread
pool (task-oriented rather than thread-oriented).

Concurrency is an area that I think languages like C++ and Java make
it terribly difficult to well, but then I'm on a big Erlang kick right
now, where this stuff is just a breeze.

On Thu, Jul 23, 2009 at 2:26 PM, Ozgur Ozturk<ozgur7_at_[hidden]> wrote:
> Hi,
>      I am kind of new to multithreaded programming and network programming,
> so I had some difficulty with the examples.
>      Can you confirm an epiphany I had?
> - I was thinking I had to use the asynchronous functions to handle multiple
> clients, now I understand that you can achieve same things with synchoronous
> ones w/ threads and you can write equally efficient code?.
> (It is only a different pattern; some people find the code more manageable
> the async way, since they don't need to handle threads themselves.) Is this
> new understanding true?
>
> - If no (if there is some efficiency difference), is it significant?
> (Otherwise, for the initial prototype of our software, I may use still use
> synchronous sockets w/ threads, since I am still not very comfortable with
> async.)
>
> Best regards,
> Ozgur (Oscar) Ozturk
> www.DrOzturk.com
> Phone: +1 (908) DROZGUR
> i.e,        [phone]
>
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