From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2C6851C68D; Wed, 1 May 2024 22:12:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714601573; cv=none; b=SdOfJG0MkdfcU9mdjZr5yQ4djdPneAPSq5NDGcLlze2mM976v+5Xs2rAEh/aVimFSbKVUsdIk8V42NugTD96mhkqW7z2pZmG78XddDQbiNuR4bS8Qs/mdTf+Gs7+mXa0drP9HavvxOBEtKWgfSGmL1+zPRQELcTebSUPXJeLLRs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714601573; c=relaxed/simple; bh=Ug3FQ7I2qR/RHww0ckNHp2CA4CIPVdT90yjcPc5ds/c=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=fnKuljarPxaeFXl3MREWE5BraBP+1XLccCiTFKz5MyjfJrc2hkf/ScRIE85Yle3O6IkzVGYoSWRchAFosdOa2wud4u20CO8OAy87eBBo3NPQNErgP6Hvp46So45BXT43Z2j4xSsJRIISV38YG6SDBmmbfocG226694vdSU9NjJk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gCXCc3OC; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="gCXCc3OC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6C65BC072AA; Wed, 1 May 2024 22:12:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1714601572; bh=Ug3FQ7I2qR/RHww0ckNHp2CA4CIPVdT90yjcPc5ds/c=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=gCXCc3OCNyr6+i3h4YTHs9KepSLe6n7aIrtfRjc0yAHqvWeildSuL6MWAYA37i3C5 jRrpQ4zd2eq/p/dpUQkoUYs52Cn4Im+Z+AogwoRh5jxXZityH0Y+8q0v8n0q9b7DsY JwtpslpDaQW0EehLBq5b435NxyKJe9XNoOg0CeAv+a/YK+jgnMNt5+UwLD66pAQsYv zMguRGrKKHK6EXaZpRSLWSsDhBTpdvXviFQsLg4/kbtTmDW+iUngl31YDx0HIiBfiR QMCDcKJz3jXFJJPPTw+X30RCnZC95AFPy88KOwNmF9fciBSSTWyTvN7hCtwCslDzqA QYxNlRWvDDdYg== Date: Wed, 1 May 2024 15:12:51 -0700 From: Jakub Kicinski To: Praveen Kumar Kannoju Cc: jhs@mojatatu.com, xiyou.wangcong@gmail.com, jiri@resnulli.us, davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, rajesh.sivaramasubramaniom@oracle.com, rama.nichanamatlu@oracle.com, manjunath.b.patil@oracle.com Subject: Re: [PATCH RFC] net/sched: adjust device watchdog timer to detect stopped queue at right time Message-ID: <20240501151251.2eccb4d0@kernel.org> In-Reply-To: <20240430140010.5005-1-praveen.kannoju@oracle.com> References: <20240430140010.5005-1-praveen.kannoju@oracle.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 30 Apr 2024 19:30:10 +0530 Praveen Kumar Kannoju wrote: > Applications are sensitive to long network latency, particularly > heartbeat monitoring ones. Longer the tx timeout recovery higher the > risk with such applications on a production machines. This patch > remedies, yet honoring device set tx timeout. > > Modify watchdog next timeout to be shorter than the device specified. > Compute the next timeout be equal to device watchdog timeout less the > how long ago queue stop had been done. At next watchdog timeout tx > timeout handler is called into if still in stopped state. Either called > or not called, restore the watchdog timeout back to device specified. Idea makes sense, some comments on the code below. > diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c > index 4a2c763e2d11..64e31f8b4ac1 100644 > --- a/net/sched/sch_generic.c > +++ b/net/sched/sch_generic.c > @@ -506,18 +506,25 @@ static void dev_watchdog(struct timer_list *t) > unsigned int timedout_ms = 0; > unsigned int i; > unsigned long trans_start; > + unsigned long next_check = 0; > + unsigned long current_jiffies; > > for (i = 0; i < dev->num_tx_queues; i++) { > struct netdev_queue *txq; > + current_jiffies = jiffies; Not sure why you save current jiffies. > txq = netdev_get_tx_queue(dev, i); > trans_start = READ_ONCE(txq->trans_start); > - if (netif_xmit_stopped(txq) && > - time_after(jiffies, (trans_start + > - dev->watchdog_timeo))) { > - timedout_ms = jiffies_to_msecs(jiffies - trans_start); > - atomic_long_inc(&txq->trans_timeout); > - break; > + if (netif_xmit_stopped(txq)) { please use continue instead of adding another indentation level > + if (time_after(current_jiffies, (trans_start + wrap at 80 characters > + dev->watchdog_timeo))) { > + timedout_ms = jiffies_to_msecs(current_jiffies - > + trans_start); > + atomic_long_inc(&txq->trans_timeout); > + break; > + } > + next_check = trans_start + dev->watchdog_timeo - > + current_jiffies; this will give us "next_check" for last queue. Let's instead find the oldest trans_start in the loop. Do: unsigned long oldest_start = jiffies; then in the loop: oldest_start = min(...) > } > } > > @@ -530,9 +537,11 @@ static void dev_watchdog(struct timer_list *t) > dev->netdev_ops->ndo_tx_timeout(dev, i); > netif_unfreeze_queues(dev); > } > + if (!next_check) > + next_check = dev->watchdog_timeo; > if (!mod_timer(&dev->watchdog_timer, > round_jiffies(jiffies + > - dev->watchdog_timeo))) > + next_check))) then here you just need to swap jiffies for oldest_start > release = false; > } > }