3.14-stable review patch. If anyone has any objections, please let me know.
------------------ From: David Rientjes <[email protected]> commit 14a4e2141e24304fff2c697be6382ffb83888185 upstream. Commit 9f1b868a13ac ("mm: thp: khugepaged: add policy for finding target node") improved the previous khugepaged logic which allocated a transparent hugepages from the node of the first page being collapsed. However, it is still possible to collapse pages to remote memory which may suffer from additional access latency. With the current policy, it is possible that 255 pages (with PAGE_SHIFT == 12) will be collapsed remotely if the majority are allocated from that node. When zone_reclaim_mode is enabled, it means the VM should make every attempt to allocate locally to prevent NUMA performance degradation. In this case, we do not want to collapse hugepages to remote nodes that would suffer from increased access latency. Thus, when zone_reclaim_mode is enabled, only allow collapsing to nodes with RECLAIM_DISTANCE or less. There is no functional change for systems that disable zone_reclaim_mode. Signed-off-by: David Rientjes <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Andrea Arcangeli <[email protected]> Acked-by: Vlastimil Babka <[email protected]> Acked-by: Mel Gorman <[email protected]> Cc: Rik van Riel <[email protected]> Cc: "Kirill A. Shutemov" <[email protected]> Cc: Bob Liu <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Mel Gorman <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- mm/huge_memory.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2273,6 +2273,30 @@ static void khugepaged_alloc_sleep(void) static int khugepaged_node_load[MAX_NUMNODES]; +static bool khugepaged_scan_abort(int nid) +{ + int i; + + /* + * If zone_reclaim_mode is disabled, then no extra effort is made to + * allocate memory locally. + */ + if (!zone_reclaim_mode) + return false; + + /* If there is a count for this node already, it must be acceptable */ + if (khugepaged_node_load[nid]) + return false; + + for (i = 0; i < MAX_NUMNODES; i++) { + if (!khugepaged_node_load[i]) + continue; + if (node_distance(nid, i) > RECLAIM_DISTANCE) + return true; + } + return false; +} + #ifdef CONFIG_NUMA static int khugepaged_find_target_node(void) { @@ -2589,6 +2613,8 @@ static int khugepaged_scan_pmd(struct mm * hit record. */ node = page_to_nid(page); + if (khugepaged_scan_abort(node)) + goto out_unmap; khugepaged_node_load[node]++; VM_BUG_ON_PAGE(PageCompound(page), page); if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
