On 04/24/2014 03:37 AM, Mel Gorman wrote: > On Mon, Apr 21, 2014 at 11:24:26AM -0700, Dave Hansen wrote: >> +This will cause us to do the global flush for more cases. >> +Lowering it to 0 will disable the use of the individual flushes. >> +Setting it to 1 is a very conservative setting and it should >> +never need to be 0 under normal circumstances. >> + >> +Despite the fact that a single individual flush on x86 is >> +guaranteed to flush a full 2MB, hugetlbfs always uses the full >> +flushes. THP is treated exactly the same as normal memory. >> + > > You are the second person that told me this and I felt the manual was > unclear on this subject. I was told that it might be a documentation bug > but because this discussion was in a bar I completely failed to follow up > on it. Specifically this part in 4.10.2.3 caused me problems when I last > looked at the area. <snip> My understanding comes from "4.10.4.2 Recommended Invalidation": • If software modifies a paging-structure entry that identifies the final page frame for a page number (either a PTE or a paging-structure entry in which the PS flag is 1), it should execute INVLPG for any linear address with a page number whose translation uses that PTE. 2 and especially the footnote: 2. One execution of INVLPG is sufficient even for a page with size greater than 4 KBytes. I do agree that it's ambiguous at best. I'll go see if anybody cares to update that bit. -- 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>