Return-path: Received: from mail-wg0-f42.google.com ([74.125.82.42]:34899 "EHLO mail-wg0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759227AbbBINr6 convert rfc822-to-8bit (ORCPT ); Mon, 9 Feb 2015 08:47:58 -0500 Received: by mail-wg0-f42.google.com with SMTP id x13so26878487wgg.1 for ; Mon, 09 Feb 2015 05:47:56 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: <1422537297.21689.15.camel@edumazet-glaptop2.roam.corp.google.com> <1422628835.21689.95.camel@edumazet-glaptop2.roam.corp.google.com> <1422903136.21689.114.camel@edumazet-glaptop2.roam.corp.google.com> <1422926330.21689.138.camel@edumazet-glaptop2.roam.corp.google.com> <1422973660.907.10.camel@edumazet-glaptop2.roam.corp.google.com> <1423051045.907.108.camel@edumazet-glaptop2.roam.corp.google.com> <1423053531.907.115.camel@edumazet-glaptop2.roam.corp.google.com> <1423055810.907.125.camel@edumazet-glaptop2.roam.corp.google.com> <1423056591.907.130.camel@edumazet-glaptop2.roam.corp.google.com> <1423084303.31870.15.camel@edumazet-glaptop2.roam.corp.google.com> <1423141038.31870.38.camel@edumazet-glaptop2.roam.corp.google.com> <1423142342.31870.49.camel@edumazet-glaptop2.roam.corp.google.com> <1423147286.31870.59.camel@edumazet-glaptop2.roam.corp.google.com> <1423156205.31870.86.camel@edumazet-glaptop2.roam.corp.google.com> <1423230001.31870.128.camel@edumazet-glaptop2.roam.corp.google.com> <1423230785.31870.131.camel@edumazet-glaptop2.roam.corp.google.com> Date: Mon, 9 Feb 2015 14:47:56 +0100 Message-ID: (sfid-20150209_144808_527275_6AEFFBCC) Subject: Re: Throughput regression with `tcp: refine TSO autosizing` From: Michal Kazior To: Eric Dumazet Cc: Neal Cardwell , linux-wireless , Network Development , Eyal Perry Content-Type: text/plain; charset=UTF-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: On 6 February 2015 at 15:09, Michal Kazior wrote: > On 6 February 2015 at 14:53, Eric Dumazet wrote: >> On Fri, 2015-02-06 at 05:40 -0800, Eric Dumazet wrote: >> >>> tcp_wfree() could maintain in tp->tx_completion_delay_ms an EWMA >>> of TX completion delay. But this would require yet another expensive >>> call to ktime_get() if HZ < 1000. >>> >>> Then tcp_write_xmit() could use it to adjust : >>> >>> limit = max(2 * skb->truesize, sk->sk_pacing_rate >> 9); >>> >>> to >>> >>> amount = (2 + tp->tx_completion_delay_ms) * sk->sk_pacing_rate >>> >>> limit = max(2 * skb->truesize, amount / 1000); >>> >>> I'll cook a patch. >> >> Hmm... doing this in all protocols would be too expensive, >> and we do not want to include time spent in qdiscs. >> >> wifi could eventually do that, providing in skb->tx_completion_delay_us >> the time spent in wifi driver. >> >> This way, we would have no penalty for network devices doing normal skb >> orphaning (loopback interface, ethernet, ...) > > I'll play around with this idea and report back later. I'm able to get 600mbps with 5 flows and 250mbps with 1 flow, i.e. same as before the regression. I'm attaching the patch at the end of my mail - is this approach viable? I wonder if there's anything that can be done to allow 600mbps (line rate) on 1 flow with ath10k without tweaking tcp_limit_output_bytes (you can't expect end-users to tweak this). Perhaps tcp_limit_output_bytes should also consider tx_completion_delay, e.g.: amount = sk->sk_tx_completion_delay_us; amount *= sk->sk_pacing_rate >> 10; limit = max(2 * skb->truesize, amount >> 10); max_limit = sysctl_tcp_limit_output_bytes; max_limit *= 1 + (sk->sk_tx_completion_delay_us / USEC_PER_MSEC); limit = min(u32, limit, max_limit); With this I get ~400mbps on 1 flow. If I add the original 1ms extra delay from your formula to tx_completion_delay I fill in ath10k I get nearly line rate in 1 flow (almost 600mbps; it hops between 570-620). Decreasing tcp_limit_output_bytes decreases throughput (e.g. 64K gives 300mbps, 32K gives 180mbps, 16K gives 110mbps). Multiple flows in iperf seem unbalanced with 128K limit, but look okay with 32K). Michał diff --git a/drivers/net/wireless/ath/ath10k/core.h b/drivers/net/wireless/ath/ath10k/core.h index 3be3a59..4ff0ae8 100644 --- a/drivers/net/wireless/ath/ath10k/core.h +++ b/drivers/net/wireless/ath/ath10k/core.h @@ -82,6 +82,7 @@ struct ath10k_skb_cb { dma_addr_t paddr; u8 eid; u8 vdev_id; + ktime_t stamp; struct { u8 tid; diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c index 15e47f4..5efb2a7 100644 --- a/drivers/net/wireless/ath/ath10k/mac.c +++ b/drivers/net/wireless/ath/ath10k/mac.c @@ -2620,6 +2620,7 @@ static void ath10k_tx(struct ieee80211_hw *hw, if (info->flags & IEEE80211_TX_CTL_NO_CCK_RATE) ath10k_dbg(ar, ATH10K_DBG_MAC, "IEEE80211_TX_CTL_NO_CCK_RATE\n"); + ATH10K_SKB_CB(skb)->stamp = ktime_get(); ATH10K_SKB_CB(skb)->htt.is_offchan = false; ATH10K_SKB_CB(skb)->htt.tid = ath10k_tx_h_get_tid(hdr); ATH10K_SKB_CB(skb)->vdev_id = ath10k_tx_h_get_vdev_id(ar, vif); diff --git a/drivers/net/wireless/ath/ath10k/txrx.c b/drivers/net/wireless/ath/ath10k/txrx.c index 3f00cec..0d5539b 100644 --- a/drivers/net/wireless/ath/ath10k/txrx.c +++ b/drivers/net/wireless/ath/ath10k/txrx.c @@ -15,6 +15,7 @@ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ +#include #include "core.h" #include "txrx.h" #include "htt.h" @@ -82,6 +83,13 @@ void ath10k_txrx_tx_unref(struct ath10k_htt *htt, ath10k_report_offchan_tx(htt->ar, msdu); + if (msdu->sk) { + ACCESS_ONCE(msdu->sk->sk_tx_completion_delay_us) = + ktime_to_ns(ktime_sub(ktime_get(), + skb_cb->stamp)) / + NSEC_PER_USEC; + } + info = IEEE80211_SKB_CB(msdu); memset(&info->status, 0, sizeof(info->status)); trace_ath10k_txrx_tx_unref(ar, tx_done->msdu_id); diff --git a/include/net/sock.h b/include/net/sock.h index 2210fec..6b15d71 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -390,6 +390,7 @@ struct sock { int sk_wmem_queued; gfp_t sk_allocation; u32 sk_pacing_rate; /* bytes per second */ + u32 sk_tx_completion_delay_us; u32 sk_max_pacing_rate; netdev_features_t sk_route_caps; netdev_features_t sk_route_nocaps; diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 65caf8b..5e249bf 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1996,6 +1996,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, max_segs = tcp_tso_autosize(sk, mss_now); while ((skb = tcp_send_head(sk))) { unsigned int limit; + unsigned int amount; tso_segs = tcp_init_tso_segs(sk, skb, mss_now); BUG_ON(!tso_segs); @@ -2053,7 +2054,9 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, * of queued bytes to ensure line rate. * One example is wifi aggregation (802.11 AMPDU) */ - limit = max(2 * skb->truesize, sk->sk_pacing_rate >> 10); + amount = sk->sk_tx_completion_delay_us * + (sk->sk_pacing_rate >> 10); + limit = max(2 * skb->truesize, amount >> 10); limit = min_t(u32, limit, sysctl_tcp_limit_output_bytes); if (atomic_read(&sk->sk_wmem_alloc) > limit) {