On Tue, 1 Oct 2013 22:47:36 -0700 (PDT) David Rientjes <rientjes@xxxxxxxxxx> wrote: > On Mon, 30 Sep 2013, Andrew Morton wrote: > > > > Nobody uses the pvec->cold argument of pagevec and it's also unreasonable for > > > pages in pagevec released as cold page, so drop the cold argument from pagevec. > > > > Is it unreasonable? I'd say it's unreasonable to assume that all pages > > in all cases are likely to be cache-hot. Example: what if the pages > > are being truncated and were found to be on the inactive LRU, > > unreferenced? > > > > A useful exercise would be to go through all those pagevec_init() sites > > and convince ourselves that the decision at each place was the correct > > one. > > > > Agreed, and the "cold" argument to release_pages() becomes a no-op if this > patch is merged meaning that anything released through it will > automatically go to the start of the pcp lists. If the pages aren't hot > then this is exactly the opposite of what we wanted to do; the fact that > the pvec length doesn't take into account the size of cpu cache can almost > guarantee that everything isn't cache hot. The hot/cold pages code was very marginal when we first merged it and I suspect it has rotted since. It would be a useful exercise for someone to disable it then run some benchmarks with a view to removing it all. But the problem I have with this approach is perhaps the code *could* become effective if some careful maintenance work was done on it - we should at least get the hot/cold decisions optimised before making a decision about the overall desirability of keeping it. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
