From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id B00ABA0C4B; Mon, 8 Nov 2021 11:13:47 +0100 (CET) Received: from [217.70.189.124] (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 7718340E03; Mon, 8 Nov 2021 11:13:47 +0100 (CET) Received: from mail-wm1-f47.google.com (mail-wm1-f47.google.com [209.85.128.47]) by mails.dpdk.org (Postfix) with ESMTP id 299FA40151 for ; Mon, 8 Nov 2021 11:13:46 +0100 (CET) Received: by mail-wm1-f47.google.com with SMTP id f7-20020a1c1f07000000b0032ee11917ceso11231205wmf.0 for ; Mon, 08 Nov 2021 02:13:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=v3YCQoYAKNt+kKn0dxbrNHohbj6Lipq9lqV2u6fGgXY=; b=Co4zd7IVsZixgQ5RvoYoy4JhKr10v5ry10lkhZrh63pTY6JkKXsLgN7jtAn2BpPcIo 7SSJVAKAIO6PHWbcZ/IgG9J32aE6jTaPguMrGrtYbm4rijgCNWz6/S3KZhT0N9HOt8DW qhnDFzGLZ+2DeU3FSSa1REgmkLeAc5RIv+aw6bxYyPDDpCupU2E3gp4b0C1HwuGqGkPV mZYHX5lwdPTv7D1/ksysCOIizwEnKA2bMZkH/Y6kYEmXqfLQxAnDmRUkokZ8GDoUtOPW YYWm1LPQUVNvQsjW/HozF4uM1UCVl7iR7rg2zjvXhWnEYa9VmXknBnBNYp5fQfYJYoWJ 7qGA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=v3YCQoYAKNt+kKn0dxbrNHohbj6Lipq9lqV2u6fGgXY=; b=OZ623I/IRMRosFb7nJ1Yk/G8mXSsw6jm19N7AcZs+slbYC4WIX6Uo1Sx49PMtecBtl wquOcrkIQxzQ8NzhaAI2mAT1mynB9ZwQkWQ+ffH1UsCuaoBn7Q2yYYIx8yj53mhOjIxd syeK+Bn+oHuI90zkIvM+UsQ57BrJvk3gwBXq7m071aLPMHjfTHV4kYDOA+pXtzi+V39r QF/ab0CB2Tmqj591ujyGOi5/cW79khgHUPC+58gbqj7yFefcGUmpdw57Wu06CrgpcF7b WNKMnAtUZP6IEup7FZAqbSqylih7l/5qXcyj57/vAjA1Rb7QR2a6hw12ywuH+9lmRAK1 C4YA== X-Gm-Message-State: AOAM530W9rceIs+dz7sgIO6j6Il4pOqtFODEipsULr3f1q1hxAIzi9oB MJxHHHqZdUdkU/qk+ub7Cjc= X-Google-Smtp-Source: ABdhPJxfUqO85moMO/jmDs04MhQzbj6Vd95wiChm/BTNhf++2zFmF/hevxSuIt+v6Zypl9qvFuiKIg== X-Received: by 2002:a7b:c08a:: with SMTP id r10mr50131552wmh.184.1636366425902; Mon, 08 Nov 2021 02:13:45 -0800 (PST) Received: from tucornea-dev-machine.localdomain ([193.226.172.44]) by smtp.gmail.com with ESMTPSA id o3sm16389315wms.10.2021.11.08.02.13.45 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 08 Nov 2021 02:13:45 -0800 (PST) From: Tudor Cornea To: thomas@monjalon.net Cc: stephen@networkplumber.org, ferruh.yigit@intel.com, dev@dpdk.org, Tudor Cornea Date: Mon, 8 Nov 2021 12:13:33 +0200 Message-Id: <1636366413-57455-1-git-send-email-tudor.cornea@gmail.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1635868273-69843-1-git-send-email-tudor.cornea@gmail.com> References: <1635868273-69843-1-git-send-email-tudor.cornea@gmail.com> Subject: [dpdk-dev] [PATCH v3] kni: allow configuring the kni thread granularity X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" The Kni kthreads seem to be re-scheduled at a granularity of roughly 1 millisecond right now, which seems to be insufficient for performing tests involving a lot of control plane traffic. Even if KNI_KTHREAD_RESCHEDULE_INTERVAL is set to 5 microseconds, it seems that the existing code cannot reschedule at the desired granularily, due to precision constraints of schedule_timeout_interruptible(). In our use case, we leverage the Linux Kernel for control plane, and it is not uncommon to have 60K - 100K pps for some signaling protocols. Since we are not in atomic context, the usleep_range() function seems to be more appropriate for being able to introduce smaller controlled delays, in the range of 5-10 microseconds. Upon reading the existing code, it would seem that this was the original intent. Adding sub-millisecond delays, seems unfeasible with a call to schedule_timeout_interruptible(). KNI_KTHREAD_RESCHEDULE_INTERVAL 5 /* us */ schedule_timeout_interruptible( usecs_to_jiffies(KNI_KTHREAD_RESCHEDULE_INTERVAL)); Below, we attempted a brief comparison between the existing implementation, which uses schedule_timeout_interruptible() and usleep_range(). We attempt to measure the CPU usage, and RTT between two Kni interfaces, which are created on top of vmxnet3 adapters, connected by a vSwitch. insmod rte_kni.ko kthread_mode=single carrier=on schedule_timeout_interruptible(usecs_to_jiffies(5)) kni_single CPU Usage: 2-4 % [root@localhost ~]# ping 1.1.1.2 -I eth1 PING 1.1.1.2 (1.1.1.2) from 1.1.1.1 eth1: 56(84) bytes of data. 64 bytes from 1.1.1.2: icmp_seq=1 ttl=64 time=2.70 ms 64 bytes from 1.1.1.2: icmp_seq=2 ttl=64 time=1.00 ms 64 bytes from 1.1.1.2: icmp_seq=3 ttl=64 time=1.99 ms 64 bytes from 1.1.1.2: icmp_seq=4 ttl=64 time=0.985 ms 64 bytes from 1.1.1.2: icmp_seq=5 ttl=64 time=1.00 ms usleep_range(5, 10) kni_single CPU usage: 50% 64 bytes from 1.1.1.2: icmp_seq=1 ttl=64 time=0.338 ms 64 bytes from 1.1.1.2: icmp_seq=2 ttl=64 time=0.150 ms 64 bytes from 1.1.1.2: icmp_seq=3 ttl=64 time=0.123 ms 64 bytes from 1.1.1.2: icmp_seq=4 ttl=64 time=0.139 ms 64 bytes from 1.1.1.2: icmp_seq=5 ttl=64 time=0.159 ms usleep_range(20, 50) kni_single CPU usage: 24% 64 bytes from 1.1.1.2: icmp_seq=1 ttl=64 time=0.202 ms 64 bytes from 1.1.1.2: icmp_seq=2 ttl=64 time=0.170 ms 64 bytes from 1.1.1.2: icmp_seq=3 ttl=64 time=0.171 ms 64 bytes from 1.1.1.2: icmp_seq=4 ttl=64 time=0.248 ms 64 bytes from 1.1.1.2: icmp_seq=5 ttl=64 time=0.185 ms usleep_range(50, 100) kni_single CPU usage: 13% 64 bytes from 1.1.1.2: icmp_seq=1 ttl=64 time=0.537 ms 64 bytes from 1.1.1.2: icmp_seq=2 ttl=64 time=0.257 ms 64 bytes from 1.1.1.2: icmp_seq=3 ttl=64 time=0.231 ms 64 bytes from 1.1.1.2: icmp_seq=4 ttl=64 time=0.143 ms 64 bytes from 1.1.1.2: icmp_seq=5 ttl=64 time=0.200 ms usleep_range(100, 200) kni_single CPU usage: 7% 64 bytes from 1.1.1.2: icmp_seq=1 ttl=64 time=0.716 ms 64 bytes from 1.1.1.2: icmp_seq=2 ttl=64 time=0.167 ms 64 bytes from 1.1.1.2: icmp_seq=3 ttl=64 time=0.459 ms 64 bytes from 1.1.1.2: icmp_seq=4 ttl=64 time=0.455 ms 64 bytes from 1.1.1.2: icmp_seq=5 ttl=64 time=0.252 ms usleep_range(1000, 1100) kni_single CPU usage: 2% 64 bytes from 1.1.1.2: icmp_seq=1 ttl=64 time=2.22 ms 64 bytes from 1.1.1.2: icmp_seq=2 ttl=64 time=1.17 ms 64 bytes from 1.1.1.2: icmp_seq=3 ttl=64 time=1.17 ms 64 bytes from 1.1.1.2: icmp_seq=4 ttl=64 time=1.17 ms 64 bytes from 1.1.1.2: icmp_seq=5 ttl=64 time=1.15 ms Upon testing, usleep_range(1000, 1100) seems roughly equivalent in latency and cpu usage to the variant with schedule_timeout_interruptible(), while usleep_range(100, 200) seems to give a decent tradeoff between latency and cpu usage, while allowing users to tweak the limits for improved precision if they have such use cases. Disabling RTE_KNI_PREEMPT_DEFAULT, interestingly seems to lead to a softlockup on my kernel. Kernel panic - not syncing: softlockup: hung tasks CPU: 0 PID: 1226 Comm: kni_single Tainted: G W O 3.10 #1 [] dump_stack+0x19/0x1b [] panic+0xcd/0x1e0 [] watchdog_timer_fn+0x160/0x160 [] __run_hrtimer.isra.4+0x42/0xd0 [] hrtimer_interrupt+0xe7/0x1f0 [] smp_apic_timer_interrupt+0x67/0xa0 [] apic_timer_interrupt+0x6d/0x80 References: [1] https://www.kernel.org/doc/Documentation/timers/timers-howto.txt Signed-off-by: Tudor Cornea --- v3: * Fixed unwrapped commit description warning * Changed from hrtimers to Linux High Precision Timers in docs * Added two tabs at the beginning of the new params description. Stephen correctly pointed out that the descriptions of the parameters for the Kni module are nonstandard w.r.t existing kernel code. I was thinking to preserve compatibility with the existing parameters of the Kni module for the moment, while an additional clean-up patch could format the descriptions to be closer to the kernel standard. v2: * Fixed some spelling errors --- doc/guides/prog_guide/kernel_nic_interface.rst | 33 +++++++++++++++++++++++ kernel/linux/kni/kni_dev.h | 2 +- kernel/linux/kni/kni_misc.c | 36 +++++++++++++++++++++++--- 3 files changed, 66 insertions(+), 5 deletions(-) diff --git a/doc/guides/prog_guide/kernel_nic_interface.rst b/doc/guides/prog_guide/kernel_nic_interface.rst index 1ce03ec..fce3667 100644 --- a/doc/guides/prog_guide/kernel_nic_interface.rst +++ b/doc/guides/prog_guide/kernel_nic_interface.rst @@ -56,6 +56,10 @@ can be specified when the module is loaded to control its behavior: off Interfaces will be created with carrier state set to off. on Interfaces will be created with carrier state set to on. (charp) + parm: min_scheduling_interval: "Kni thread min scheduling interval (default=100 microseconds): + (long) + parm: max_scheduling_interval: "Kni thread max scheduling interval (default=200 microseconds): + (long) Loading the ``rte_kni`` kernel module without any optional parameters is the typical way a DPDK application gets packets into and out of the kernel @@ -174,6 +178,35 @@ To set the default carrier state to *off*: If the ``carrier`` parameter is not specified, the default carrier state of KNI interfaces will be set to *off*. +KNI Kthread Scheduling +~~~~~~~~~~~~~~~~~~~~~~ + +The ``min_scheduling_interval`` and ``max_scheduling_interval`` parameters +control the rescheduling interval of the KNI kthreads. + +This might be useful if we have use cases in which we require improved +latency or performance for control plane traffic. + +The implementation is backed by Linux High Precision Timers, and uses ``usleep_range``. +Hence, it will have the same granularity constraints as this Linux subsystem. + +For Linux High Precision Timers, you can check the following resource: `Kernel Timers `_ + +To set the ``min_scheduling_interval`` to a value of 100 microseconds: + +.. code-block:: console + + # insmod /kernel/linux/kni/rte_kni.ko min_scheduling_interval=100 + +To set the ``max_scheduling_interval`` to a value of 200 microseconds: + +.. code-block:: console + + # insmod /kernel/linux/kni/rte_kni.ko max_scheduling_interval=200 + +If the ``min_scheduling_interval`` and ``max_scheduling_interval`` parameters are +not specified, the default interval limits will be set to *100* and *200* respectively. + KNI Creation and Deletion ------------------------- diff --git a/kernel/linux/kni/kni_dev.h b/kernel/linux/kni/kni_dev.h index c15da311..bb4d891 100644 --- a/kernel/linux/kni/kni_dev.h +++ b/kernel/linux/kni/kni_dev.h @@ -27,7 +27,7 @@ #include #include -#define KNI_KTHREAD_RESCHEDULE_INTERVAL 5 /* us */ +#define KNI_KTHREAD_MAX_RESCHEDULE_INTERVAL 1000000 /* us */ #define MBUF_BURST_SZ 32 diff --git a/kernel/linux/kni/kni_misc.c b/kernel/linux/kni/kni_misc.c index 2b464c4..1bfa33f 100644 --- a/kernel/linux/kni/kni_misc.c +++ b/kernel/linux/kni/kni_misc.c @@ -41,6 +41,12 @@ static uint32_t multiple_kthread_on; static char *carrier; uint32_t kni_dflt_carrier; +#ifdef RTE_KNI_PREEMPT_DEFAULT +/* Kni thread scheduling interval */ +static long min_scheduling_interval = 100; /* us */ +static long max_scheduling_interval = 200; /* us */ +#endif + #define KNI_DEV_IN_USE_BIT_NUM 0 /* Bit number for device in use */ static int kni_net_id; @@ -130,8 +136,7 @@ kni_thread_single(void *data) up_read(&knet->kni_list_lock); #ifdef RTE_KNI_PREEMPT_DEFAULT /* reschedule out for a while */ - schedule_timeout_interruptible( - usecs_to_jiffies(KNI_KTHREAD_RESCHEDULE_INTERVAL)); + usleep_range(min_scheduling_interval, max_scheduling_interval); #endif } @@ -150,8 +155,7 @@ kni_thread_multiple(void *param) kni_net_poll_resp(dev); } #ifdef RTE_KNI_PREEMPT_DEFAULT - schedule_timeout_interruptible( - usecs_to_jiffies(KNI_KTHREAD_RESCHEDULE_INTERVAL)); + usleep_range(min_scheduling_interval, max_scheduling_interval); #endif } @@ -593,6 +597,16 @@ kni_init(void) else pr_debug("Default carrier state set to on.\n"); +#ifdef RTE_KNI_PREEMPT_DEFAULT + if (min_scheduling_interval < 0 || max_scheduling_interval < 0 || + min_scheduling_interval > KNI_KTHREAD_MAX_RESCHEDULE_INTERVAL || + max_scheduling_interval > KNI_KTHREAD_MAX_RESCHEDULE_INTERVAL || + min_scheduling_interval >= max_scheduling_interval) { + pr_err("Invalid parameters for scheduling interval\n"); + return -EINVAL; + } +#endif + #ifdef HAVE_SIMPLIFIED_PERNET_OPERATIONS rc = register_pernet_subsys(&kni_net_ops); #else @@ -659,3 +673,17 @@ MODULE_PARM_DESC(carrier, "\t\ton Interfaces will be created with carrier state set to on.\n" "\t\t" ); + +#ifdef RTE_KNI_PREEMPT_DEFAULT +module_param(min_scheduling_interval, long, 0644); +MODULE_PARM_DESC(min_scheduling_interval, +"\t\tKni thread min scheduling interval (default=100 microseconds):\n" +"\t\t" +); + +module_param(max_scheduling_interval, long, 0644); +MODULE_PARM_DESC(max_scheduling_interval, +"\t\tKni thread max scheduling interval (default=200 microseconds):\n" +"\t\t" +); +#endif -- 2.7.4