On Wed, 28 Feb 2007, Ingo Molnar wrote: > > * Davide Libenzi <davidel@xmailserver.org> wrote: > > > Why can't aio_* be implemented with *simple* (or parallel/unrelated) > > syscall submit w/out the burden of a complex, limiting and heavy API > > there are so many variants of what people think 'asynchronous IO' should > look like - i'd not like to limit them. I agree that once a particular > syslet script becomes really popular, it might (and should) in fact be > pushed into a separate system call. > > But i also agree that a one-shot-syscall sys_async() syscall could be > done too - for those uses where only a single system call is needed and > where the fetching of a single uatom would be small but nevertheless > unnecessary overhead. A one-shot async syscall needs to get /8/ > parameters (the syscall nr is the seventh parameter and the return code > of the nested syscall is the eighth). So at least two parameters will > have to be passed in indirectly and validated, and 32/64-bit compat > conversions added, etc. anyway!
At this point, given how threadlets can be easily/effectively dispatched from userspace, I'd argue the presence of either single/parallel or syslet submission altogether. Threadlets allows you to code chains *way* more naturally than syslets, and since they basically are like functions calls in the fast path, they can be used even for single/parallel submissions. No compat code required (ok, besides the trivial async_wait). My point is, the syslet infrastructure is expensive for the kernel in terms of compat, and extra code added to handle the cond/jumps/etc. Is also non-trivial to use from userspace. Are those big performance advantages there to justify its existence? I doubt that the price of a sysenter is a lot bigger than a atom decoding, but I'm looking forward in being proven wrong by real life performance numbers ;) - Davide - 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/
