On 19 January 2005 09:45, Ben Rudiak-Gould wrote:
Glynn Clements wrote:
Ben Rudiak-Gould wrote:
GHC really needs non-blocking I/O to support its thread model, and memory-mapped I/O always blocks. > If, by "blocks", you mean that execution will be suspended until the data has been read from the device into the buffer cache, then Unix non-blocking I/O (i.e. O_NONBLOCK) also blocks.
Okay, my ignorance of Posix is showing again. Is it currently the case, then, that every GHC thread will stop running while a disk read is in progress in any thread? Is this true on all platforms?
It's true on Unix-like systems, I believe. Even with -threaded. It might not be true on Win32.
(By the way, are the GHC folks aware that the description of Win32 I/O at [2] is wrong? It seems to assume that ReadFile doesn't return until the buffer is full.)
I don't think that description corresponds with the implementation, but then I'm not terribly familiar with that part of the code. It doesn't get used when -threaded is on. Cheers, Simon