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 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. [...] -- 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>