• Shaohua Li's avatar
    net: don't wait for order-3 page allocation · fb05e7a8
    Shaohua Li authored
    We saw excessive direct memory compaction triggered by skb_page_frag_refill.
    This causes performance issues and add latency. Commit 5640f768
    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 <edumazet@google.com>
    Cc: Chris Mason <clm@fb.com>
    Cc: Debabrata Banerjee <dbavatar@gmail.com>
    Signed-off-by: default avatarShaohua Li <shli@fb.com>
    Acked-by: default avatarEric Dumazet <edumazet@google.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    fb05e7a8
sock.c 72.7 KB