On Thu, 2015-06-11 at 15:27 -0700, Shaohua Li wrote:
> 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.
>
> The mellanox driver does similar thing, if this is accepted, we must fix
> the driver too.
>
> V2: make the changelog clearer
>
> Cc: Eric Dumazet <eduma...@google.com>
> Signed-off-by: Shaohua Li <s...@fb.com>
> ---
> net/core/sock.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 292f422..e9855a4 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1883,7 +1883,7 @@ bool skb_page_frag_refill(unsigned int sz, struct
> page_frag *pfrag, gfp_t gfp)
>
> pfrag->offset = 0;
> if (SKB_FRAG_PAGE_ORDER) {
> - pfrag->page = alloc_pages(gfp | __GFP_COMP |
> + pfrag->page = alloc_pages((gfp & ~__GFP_WAIT) | __GFP_COMP |
> __GFP_NOWARN | __GFP_NORETRY,
> SKB_FRAG_PAGE_ORDER);
> if (likely(pfrag->page)) {
OK, now what about alloc_skb_with_frags() ?
This should have same problem right ?
Thanks.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
