lkml.org 
[lkml]   [2020]   [Jan]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH] net: optimize cmpxchg in ip_idents_reserve
    Date
    From: Yuqi Jin <jinyuqi@huawei.com>

    atomic_try_cmpxchg is called instead of atomic_cmpxchg that can reduce
    the access number of the global variable @p_id in the loop. Let's
    optimize it for performance.

    Cc: "David S. Miller" <davem@davemloft.net>
    Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
    Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
    Cc: Eric Dumazet <edumazet@google.com>
    Cc: Yang Guo <guoyang2@huawei.com>
    Signed-off-by: Yuqi Jin <jinyuqi@huawei.com>
    Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
    ---
    net/ipv4/route.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/net/ipv4/route.c b/net/ipv4/route.c
    index 87e979f2b74a..7e28c7121c20 100644
    --- a/net/ipv4/route.c
    +++ b/net/ipv4/route.c
    @@ -496,10 +496,10 @@ u32 ip_idents_reserve(u32 hash, int segs)
    delta = prandom_u32_max(now - old);

    /* Do not use atomic_add_return() as it makes UBSAN unhappy */
    + old = (u32)atomic_read(p_id);
    do {
    - old = (u32)atomic_read(p_id);
    new = old + delta + segs;
    - } while (atomic_cmpxchg(p_id, old, new) != old);
    + } while (!atomic_try_cmpxchg(p_id, &old, new));

    return new - segs;
    }
    --
    2.7.4
    \
     
     \ /
      Last update: 2020-01-15 04:24    [W:5.130 / U:0.000 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site