CODEWITHSUNDEEP
socketstcpio
ciamej
ciamej

Reputation: 7068

Are socket operations performed in parallel at the system level?

If I have a quad core machine and 4 open and active sockets is it faster to have 4 threads to read from these sockets in parallel or just have one thread that reads the sockets iteratively? Can the socket read operation be performed in parallel or is it synchronized somewhere at the system level?

Analogously, if I have 4 sockets to which I need to write some data, is it faster to have 4 threads that write to these sockets at the same time, or is it better to have one thread that does all the writing?

It seems that multiple cores should enable higher throughput (of course if the network bandwidth is not the bottleneck), however I wonder if this is the case, since after all, in the end there is only a single ethernet cord (or other medium), so at some time, all these writes will have to be synchronized anyway, and the packets will be sent sequentially...

Specifically, if I have a machine running n threads which generate requests that need to be sent to another machine is it better to open n sockets and let each thread write to it? Or is it better to synchronize all the threads and send all the data through a single socket? And on the receiving side is it better to have a single socket to read from? Or is it better to have n sockets read in parallel? What if all the readers need to be synchronized after reading anyway?

Upvotes: 1

Views: 608

Answers (1)

user207421
user207421

Reputation: 310869

Socket operations are largely asynchronous to the application; buffered; and, if you're lucky, concurrent inside the kernel: the only significant state to synchronize on is per-connection. However the rate-determining step is really the bandwidth of the network, which you can easily saturate with even just one thread. Web browsers typically open between 4 and 8 threads per Web page to fetch the HTML itself and the images etc.

Upvotes: 1

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