On 12/05/2013 02:54 PM, Mel Gorman wrote:
I think that's a better fit and a neater fix. Thanks! I think it barriers more than it needs to (definite cost vs maybe cost), the flush can be deferred until we are definitely trying to migrate and the pte case is not guaranteed to be flushed before migration due to pte_mknonnuma causing a flush in ptep_clear_flush to be avoided later. Mashing the two patches together yields this.
I think this would fix the numa migrate case. However, I believe the same issue is also present in mprotect(..., PROT_NONE) vs. compaction, for programs that trap SIGSEGV for garbage collection purposes. They could lose modifications done in-between when the pte was set to PROT_NONE, and the actual TLB flush, if compaction moves the page around in-between those two events. I don't know if this is a case we need to worry about at all, but I think the same fix would apply to that code path, so I guess we might as well make it... -- 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>