3.14-stable review patch. If anyone has any objections, please let me know.
------------------ From: Shaohua Li <[email protected]> [ Upstream commit fb05e7a89f500cfc06ae277bdc911b281928995d ] We saw excessive direct memory compaction triggered by skb_page_frag_refill. This causes performance issues and add latency. Commit 5640f7685831e0 introduces the order-3 allocation. According to the changelog, the order-3 allocation isn't a must-have but to improve performance. But direct memory compaction has high overhead. The benefit of order-3 allocation can't compensate the overhead of direct memory compaction. This patch makes the order-3 page allocation atomic. If there is no memory pressure and memory isn't fragmented, the alloction will still success, so we don't sacrifice the order-3 benefit here. If the atomic allocation fails, direct memory compaction will not be triggered, skb_page_frag_refill will fallback to order-0 immediately, hence the direct memory compaction overhead is avoided. In the allocation failure case, kswapd is waken up and doing compaction, so chances are allocation could success next time. alloc_skb_with_frags is the same. The mellanox driver does similar thing, if this is accepted, we must fix the driver too. V3: fix the same issue in alloc_skb_with_frags as pointed out by Eric V2: make the changelog clearer Cc: Eric Dumazet <[email protected]> Cc: Chris Mason <[email protected]> Cc: Debabrata Banerjee <[email protected]> Signed-off-by: Shaohua Li <[email protected]> Acked-by: Eric Dumazet <[email protected]> Signed-off-by: David S. Miller <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- net/core/skbuff.c | 4 +++- net/core/sock.c | 4 +++- 2 files changed, 6 insertions(+), 2 deletions(-) --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -368,9 +368,11 @@ refill: for (order = NETDEV_FRAG_PAGE_MAX_ORDER; ;) { gfp_t gfp = gfp_mask; - if (order) + if (order) { gfp |= __GFP_COMP | __GFP_NOWARN | __GFP_NOMEMALLOC; + gfp &= ~__GFP_WAIT; + } nc->frag.page = alloc_pages(gfp, order); if (likely(nc->frag.page)) break; --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1914,8 +1914,10 @@ bool skb_page_frag_refill(unsigned int s do { gfp_t gfp = prio; - if (order) + if (order) { gfp |= __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY; + gfp &= ~__GFP_WAIT; + } pfrag->page = alloc_pages(gfp, order); if (likely(pfrag->page)) { pfrag->offset = 0; -- 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/
