于 2011年06月21日 17:36, Mel Gorman 写道: >
Fragmentation avoidance benefits from tuning min_free_kbytes to a higher value and minimising fragmentation-related problems is crucial if THP is to allocate its necessary pages. THP tunes min_free_kbytes automatically and this value is in part related to the number of zones. At 512M on a single node machine, the recommended min_free_kbytes is close to 10% of memory which is barely tolerable as it is. At 256M, it's 17%, at 128M, it's 34% so tuning the value lower has diminishing returns as the performance impact of giving up such a high percentage of free memory is not going to be offset by reduced TLB misses. Tuning it to a higher value might make some sense if the higher min_free_kbytes was a problem but it would be much more rational to tune it as a sysctl than making it a compile-time decision.
What this patch changed is the check of total memory pages in hugepage_init(), which I don't think is suitable as a sysctl. If you mean min_free_kbytes could be tuned as a sysctl, that should be done in other patch, right? :) Thanks. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>