On Tue, Nov 20, 2012 at 11:58 AM, Fengguang Wu <fengguang.wu@xxxxxxxxx> 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>