netdev - Re: [PATCH net-next] tcp: avoid frag allocation for small frames

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 28 Nov 2011 17:04:00 -0800
From:	Vijay Subramanian <subramanian.vijay@...il.com>
To:	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] tcp: avoid frag allocation for small frames

On 22 October 2011 05:23, Eric Dumazet <eric.dumazet@...il.com> wrote:
> tcp_sendmsg() uses select_size() helper to choose skb head size when a
> new skb must be allocated.
>
> If GSO is enabled for the socket, current strategy is to force all
> payload data to be outside of headroom, in PAGE fragments.
>
> This strategy is not welcome for small packets, wasting memory.
>
> Experiments show that best results are obtained when using 2048 bytes
> for skb head (This includes the skb overhead and various headers)
>
> This patch provides better len/truesize ratios for packets sent to
> loopback device, and reduce memory needs for in-flight loopback packets,
> particularly on arches with big pages.
>
> If a sender sends many 1-byte packets to an unresponsive application,
> receiver rmem_alloc will grow faster and will stop queuing these packets
> sooner, or will collapse its receive queue to free excess memory.
>
> netperf -t TCP_RR results are improved by ~4 %, and many workloads are
> improved as well (tbench, mysql...)
>
> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
> ---
>  net/ipv4/tcp.c |    9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 704adad..cd45b44 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -897,9 +897,12 @@ static inline int select_size(const struct sock *sk, int sg)
>        int tmp = tp->mss_cache;
>
>        if (sg) {
> -               if (sk_can_gso(sk))
> -                       tmp = 0;
> -               else {
> +               if (sk_can_gso(sk)) {
> +                       /* Small frames wont use a full page:
> +                        * Payload will immediately follow tcp header.
> +                        */
> +                       tmp = SKB_WITH_OVERHEAD(2048 - MAX_TCP_HEADER);
> +               } else {
>                        int pgbreak = SKB_MAX_HEAD(MAX_TCP_HEADER);
>
>                        if (tmp >= pgbreak &&
>
>



This patch from Eric fixing select_size in tcp.c was queued to be
applied but does not seem to be in net-next tree. Was this somehow
overlooked or have I missed something?

Regards,
Vijay Subramanian
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html