On Tue, Nov 20, 2012 at 11:58 AM, Fengguang Wu <[email protected]> wrote: > >> But if cache hits were to simply update >> readahead state, it would only mean that read calls behave the same >> regardless of fadvise calls. I think that's worth pursuing. > > Here you are describing an alternative solution that will somehow trap > into the readahead code even when, for example, the application is > accessing once and again an already cached file? I'm afraid this will > add non-trivial overheads and is less attractive than the "readahead > on fadvise" solution.
Not for all cache hits, only those in state !PageUptodate, which are I/O in progress, the case that hurts. >> I ought to try to prepare a patch for this to illustrate my point. Not >> sure I'll be able to though. > > I'd be glad to materialize the readahead on fadvise proposal, if there > are no obvious negative examples/cases. I don't expect a significant performance hit if only !PageUptodate hits invoke readahead code. But I'm no kernel expert either. -- 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/
