On Thursday 15 November 2007 08:30, Paul Mackerras wrote: > Nick Piggin writes: > > What I really mean is a readv-like syscall, but one that also > > vectorises the file offset. Maybe this is useful enough as a generic > > syscall that also helps Paul's example... > > I've sometimes thought it would be useful to have a "transaction" > system call that is like a write + read combined into one: > > int transaction(int fd, char *req, size_t req_nb, > char *reply, size_t reply_nb); > > as a way to provide a general request/reply interface for special > files.
Maybe not a bad idea, though I'm not the one to ask about taste ;) In this case, it is enough for your requests to be a set of scalars (eg. file offsets), so it _could_ be handled with vectorised offsets... But in general, for special files, I guess the response is usually some structured data (that is not visible at the syscall layer). So I don't see a big problem to have a similarly arbitrarily structured request. > > Of course, I guess this all depends on whether the atomicity is an > > important requirement. If not, you can obviously just do it with > > multiple read syscalls... > > That would take N system calls instead of one, which could have a > performance impact if you need to read the counters frequently (which > I believe you do in some performance monitoring situations). That's true too. - 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/
