Synchronous memory compaction can be very expensive: it can iterate an enormous amount of memory without aborting and it can wait on page locks and writeback to complete if a pageblock cannot be defragmented.
Unfortunately, it's too expensive for pagefault for transparent hugepages and it's much better to simply fallback to pages. On 128GB machines, we find that synchronous memory compaction can take O(seconds) for a single thp fault. Signed-off-by: David Rientjes <rient...@google.com> --- mm/page_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2656,7 +2656,7 @@ rebalance: /* Wait for some write requests to complete then retry */ wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/50); goto rebalance; - } else { + } else if (!(gfp_mask & __GFP_NO_KSWAPD)) { /* * High-order allocations do not necessarily loop after * direct reclaim and reclaim/compaction depends on compaction -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/