On Tue, 18 Feb 2014, 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. > > Kernel Avg Stddev > base 7.4975 3.92% > patched 7.4174 3.26% > > Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > [Andrew: making return value PAGE_SIZE independent] > Signed-off-by: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx> So this replaces mm-readaheadc-fix-readahead-fail-for-no-local-memory-and-limit-readahead-pages.patch in -mm correct? > --- > I would like to thank Honza, David for their valuable suggestions and > patiently reviewing the patches. > > Changes in V6: > - Just limit the readahead to 2MB on 4k pages system as suggested by Linus. > and make it independent of PAGE_SIZE. > I'm not sure I understand why we want to be independent of PAGE_SIZE since we're still relying on PAGE_CACHE_SIZE. Don't you mean to do #define MAX_READAHEAD ((512*PAGE_SIZE)/PAGE_CACHE_SIZE) instead? -- 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>