On Tue, 24 Apr 2007 14:33:48 +0400 Alex Vorona <[EMAIL PROTECTED]> wrote:
> Hello David, > > Tuesday, April 24, 2007, 1:19:49 PM, you wrote: > > >> sendfile function is not just a more efficient version of a read > >> followed by a write. It reads from one fd and write to another at tha > >> same time. Please try to read 2G, and then write 2G - and how much > >> memory you will be need and how much time you will loose while reading > >> 2G from disk, but not writing them to socket. > > DS> You are correct. What I meant to say was that it's just a > DS> more efficient version of 'mmap'ing a file and then 'write'ing > DS> from the 'mmap'. The 'write' to a non-blocking socket can still > DS> 'block' on disk I/O. > > How can I avoid that blocking? Or maybe another question - how can I > deliver data from disk to network with minimal copy operations, etc. > I believe the modern way would be to use splice() system call : loop splice(from disk , to pipe) with SPLICE_F_NONBLOCK wait_event_from_epoll (pipe ready for reading) splice(from pipe, to socket) wait_event_from_epoll (socket ready for writing) But : 1) I am not sure epoll can get an event when page(s) is/are ready in pipe (ie disk delivered the page(s) to cache) 2) I am not sure splice() to socket is actually implemented with 0-copy 3) I am not sure pipe capacity (16 pages) would be enough to get a good readahead. Eric - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
