Effective optimization strategies on modern C++ compilers

Question

I\'m working on scientific code that is very performance-critical. An initial version of the code has been written and tested, and now, with profiler in hand, it\'s time to

Answer 1

My current project is a media server, with multi thread processing (C++ language). It's a time critical application, once low performance functions could cause bad results on media streaming like lost of sync, high latency, huge delays and so.

The strategy i usually use to grantee the best performance possible is to minimize the amount of heavy operational system calls that allocate or manage resources like memory, files, sockets and so.

At first i wrote my own STL, network and file manage classes.

All my containers classes ("MySTL") manage their own memory blocks to avoid multiple alloc (new) / free (delete) calls. The objects released are enqueued on a memory block pool to be reused when needed. On that way i improve performance and protect my code against memory fragmentation.

The parts of the code that need to access lower performance system resources (like files, databases, script, network write) i use separate threads for them. But not one thread for each unit (like not 1 thread for each socket), if so the operational system would lose performance while managing a high number of threads. So you can group objects of same classes to be processed on a separate thread if possible.

For example, if you have to write data to a network socket, but the socket write buffer is full, i save the data on a sendqueue buffer (which shares memory with all sockets together) to be sent on a separate thread as soon as the sockets become writeable again. At this way your main threads should never stop processing on a blocked state waiting for the operational system frees a specific resource. All the buffers released are saved and reused when needed.

After all a profile tool would be welcome to look for program bottles and shows which algorithms should be improved.

i got succeeded using that strategy once i have servers running like 500+ days on a linux machine without rebooting, with thousands users logging everyday.

[02:01] -alpha.ip.tv- Uptime: 525days 12hrs 43mins 7secs