On Thu, Jul 04, 2013 at 12:00:44PM +0200, Michal Hocko wrote: > On Thu 04-07-13 13:24:50, Joonsoo Kim wrote: > > On Thu, Jul 04, 2013 at 12:01:43AM +0800, Zhang Yanfei wrote: > > > On 07/03/2013 11:51 PM, Zhang Yanfei wrote: > > > > On 07/03/2013 11:28 PM, Michal Hocko wrote: > > > >> On Wed 03-07-13 17:34:15, Joonsoo Kim wrote: > > > >> [...] > > > >>> For one page allocation at once, this patchset makes allocator slower than > > > >>> before (-5%). > > > >> > > > >> Slowing down the most used path is a no-go. Where does this slow down > > > >> come from? > > > > > > > > I guess, it might be: for one page allocation at once, comparing to the original > > > > code, this patch adds two parameters nr_pages and pages and will do extra checks > > > > for the parameter nr_pages in the allocation path. > > > > > > > > > > If so, adding a separate path for the multiple allocations seems better. > > > > Hello, all. > > > > I modify the code for optimizing one page allocation via likely macro. > > I attach a new one at the end of this mail. > > > > In this case, performance degradation for one page allocation at once is -2.5%. > > I guess, remained overhead comes from two added parameters. > > Is it unreasonable cost to support this new feature? > > Which benchmark you are using for this testing? I use my own module which do allocation repeatedly. > > > I think that readahead path is one of the most used path, so this penalty looks > > endurable. And after supporting this feature, we can find more use cases. > > What about page faults? I would oppose that page faults are _much_ more > frequent than read ahead so you really cannot slow them down. You mean page faults for anon? Yes. I also think that it is much more frequent than read ahead. Before futher discussion, I will try to add a separate path for the multiple allocations. Thanks. > > [...] > -- > Michal Hocko > SUSE Labs > > -- > 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> -- 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>