On Wed, Jul 10, 2013 at 09:20:27AM +0800, Zhang Yanfei wrote: > 于 2013/7/10 8:31, Joonsoo Kim 写道: > > 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. > > Some days ago, I was thinking that this multiple allocation behaviour > may be useful for vmalloc allocations. So I think it is worth trying. Yeh! I think so! Thanks. > > > > > 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> > > > > > -- > Thanks. > Zhang Yanfei > > -- > 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>