lkml.org 
[lkml]   [2017]   [Feb]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Date
    Subject[PATCH 3.16 099/306] netlink: do not enter direct reclaim from netlink_dump()
    3.16.40-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Eric Dumazet <edumazet@google.com>

    commit d35c99ff77ecb2eb239731b799386f3b3637a31e upstream.

    Since linux-3.15, netlink_dump() can use up to 16384 bytes skb
    allocations.

    Due to struct skb_shared_info ~320 bytes overhead, we end up using
    order-3 (on x86) page allocations, that might trigger direct reclaim and
    add stress.

    The intent was really to attempt a large allocation but immediately
    fallback to a smaller one (order-1 on x86) in case of memory stress.

    On recent kernels (linux-4.4), we can remove __GFP_DIRECT_RECLAIM to
    meet the goal. Old kernels would need to remove __GFP_WAIT

    While we are at it, since we do an order-3 allocation, allow to use
    all the allocated bytes instead of 16384 to reduce syscalls during
    large dumps.

    iproute2 already uses 32KB recvmsg() buffer sizes.

    Alexei provided an initial patch downsizing to SKB_WITH_OVERHEAD(16384)

    Fixes: 9063e21fb026 ("netlink: autosize skb lengthes")
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Reported-by: Alexei Starovoitov <ast@kernel.org>
    Cc: Greg Thelen <gthelen@google.com>
    Reviewed-by: Greg Rose <grose@lightfleet.com>
    Acked-by: Alexei Starovoitov <ast@kernel.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    [bwh: Backported to 3.16:
    - Adjust context
    - Mask out __GFP_WAIT, as suggested]
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    net/netlink/af_netlink.c | 7 ++++---
    1 file changed, 4 insertions(+), 3 deletions(-)

    --- a/net/netlink/af_netlink.c
    +++ b/net/netlink/af_netlink.c
    @@ -2461,7 +2461,7 @@ static int netlink_recvmsg(struct kiocb
    /* Record the max length of recvmsg() calls for future allocations */
    nlk->max_recvmsg_len = max(nlk->max_recvmsg_len, len);
    nlk->max_recvmsg_len = min_t(size_t, nlk->max_recvmsg_len,
    - 16384);
    + SKB_WITH_OVERHEAD(32768));

    copied = data_skb->len;
    if (len < copied) {
    @@ -2719,9 +2719,8 @@ static int netlink_dump(struct sock *sk)
    if (alloc_min_size < nlk->max_recvmsg_len) {
    alloc_size = nlk->max_recvmsg_len;
    skb = netlink_alloc_skb(sk, alloc_size, nlk->portid,
    - GFP_KERNEL |
    - __GFP_NOWARN |
    - __GFP_NORETRY);
    + (GFP_KERNEL & ~__GFP_WAIT) |
    + __GFP_NOWARN | __GFP_NORETRY);
    }
    if (!skb) {
    alloc_size = alloc_min_size;
    \
     
     \ /
      Last update: 2017-02-16 00:37    [W:7.981 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site