On Tue 18-02-14 17:34:54, Raghavendra K T wrote: > On 02/18/2014 03:19 PM, Jan Kara wrote: > >On Tue 18-02-14 12:55:38, Raghavendra K T wrote: > >>Currently max_sane_readahead() returns zero on the cpu having no local memory node > >>which leads to readahead failure. Fix the readahead failure by returning > >>minimum of (requested pages, 512). Users running application on a memory-less cpu > >>which needs readahead such as streaming application see considerable boost in the > >>performance. > >> > >>Result: > >>fadvise experiment with FADV_WILLNEED on a PPC machine having memoryless CPU > >>with 1GB testfile ( 12 iterations) yielded around 46.66% improvement. > >> > >>fadvise experiment with FADV_WILLNEED on a x240 machine with 1GB testfile > >>32GB* 4G RAM numa machine ( 12 iterations) showed no impact on the normal > >>NUMA cases w/ patch. > > Can you try one more thing please? Compare startup time of some big > >executable (Firefox or LibreOffice come to my mind) for the patched and > >normal kernel on a machine which wasn't hit by this NUMA issue. And don't > >forget to do "echo 3 >/proc/sys/vm/drop_caches" before each test to flush > >the caches. If this doesn't show significant differences, I'm OK with the > >patch. > > > > Thanks Honza, I checked with firefox (starting to particular point).. > I do not see any difference. Both the case took around 14sec. Good. You can add my: Acked-by: Jan Kara <jack@xxxxxxx> > ( some time it is even faster.. may be because we do not do free > page calculation?. ) Hardly, that calculation is just a tiny amount of CPU time in the startup of the application. If there is really a significant difference, it might be because we don't preload stuff which isn't used in the end. Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- 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>