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From: Jakub Kicinski <kuba@kernel.org>
To: "Björn Töpel" <bjorn.topel@gmail.com>
Cc: netdev@vger.kernel.org, bpf@vger.kernel.org,
	"Björn Töpel" <bjorn.topel@intel.com>,
	magnus.karlsson@intel.com, ast@kernel.org, daniel@iogearbox.net,
	maciej.fijalkowski@intel.com, sridhar.samudrala@intel.com,
	jesse.brandeburg@intel.com, qi.z.zhang@intel.com,
	edumazet@google.com, jonathan.lemon@gmail.com,
	maximmi@nvidia.com
Subject: Re: [PATCH bpf-next v3 01/10] net: introduce preferred busy-polling
Date: Tue, 24 Nov 2020 08:21:39 -0800	[thread overview]
Message-ID: <20201124082139.77e933a6@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> (raw)
In-Reply-To: <20201119083024.119566-2-bjorn.topel@gmail.com>

On Thu, 19 Nov 2020 09:30:15 +0100 Björn Töpel wrote:
> From: Björn Töpel <bjorn.topel@intel.com>
> 
> The existing busy-polling mode, enabled by the SO_BUSY_POLL socket
> option or system-wide using the /proc/sys/net/core/busy_read knob, is
> an opportunistic. That means that if the NAPI context is not
> scheduled, it will poll it. If, after busy-polling, the budget is
> exceeded the busy-polling logic will schedule the NAPI onto the
> regular softirq handling.
> 
> One implication of the behavior above is that a busy/heavy loaded NAPI
> context will never enter/allow for busy-polling. Some applications
> prefer that most NAPI processing would be done by busy-polling.
> 
> This series adds a new socket option, SO_PREFER_BUSY_POLL, that works
> in concert with the napi_defer_hard_irqs and gro_flush_timeout
> knobs. The napi_defer_hard_irqs and gro_flush_timeout knobs were
> introduced in commit 6f8b12d661d0 ("net: napi: add hard irqs deferral
> feature"), and allows for a user to defer interrupts to be enabled and
> instead schedule the NAPI context from a watchdog timer. When a user
> enables the SO_PREFER_BUSY_POLL, again with the other knobs enabled,
> and the NAPI context is being processed by a softirq, the softirq NAPI
> processing will exit early to allow the busy-polling to be performed.
> 
> If the application stops performing busy-polling via a system call,
> the watchdog timer defined by gro_flush_timeout will timeout, and
> regular softirq handling will resume.
> 
> In summary; Heavy traffic applications that prefer busy-polling over
> softirq processing should use this option.
> 
> Example usage:
> 
>   $ echo 2 | sudo tee /sys/class/net/ens785f1/napi_defer_hard_irqs
>   $ echo 200000 | sudo tee /sys/class/net/ens785f1/gro_flush_timeout
> 
> Note that the timeout should be larger than the userspace processing
> window, otherwise the watchdog will timeout and fall back to regular
> softirq processing.
> 
> Enable the SO_BUSY_POLL/SO_PREFER_BUSY_POLL options on your socket.
> 
> Signed-off-by: Björn Töpel <bjorn.topel@intel.com>

Reviewed-by: Jakub Kicinski <kuba@kernel.org>

  parent reply	other threads:[~2020-11-24 16:21 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-19  8:30 [PATCH bpf-next v3 00/10] Introduce preferred busy-polling Björn Töpel
2020-11-19  8:30 ` [PATCH bpf-next v3 01/10] net: introduce " Björn Töpel
2020-11-24  0:04   ` Jakub Kicinski
2020-11-24  7:58     ` Björn Töpel
2020-11-24  0:11   ` Jakub Kicinski
2020-11-24  8:47     ` Björn Töpel
2020-11-24 16:21   ` Jakub Kicinski [this message]
2020-11-19  8:30 ` [PATCH bpf-next v3 02/10] net: add SO_BUSY_POLL_BUDGET socket option Björn Töpel
2020-11-24 16:21   ` Jakub Kicinski
2020-11-19  8:30 ` [PATCH bpf-next v3 03/10] xsk: add support for recvmsg() Björn Töpel
2020-11-25  6:55   ` Magnus Karlsson
2020-11-19  8:30 ` [PATCH bpf-next v3 04/10] xsk: check need wakeup flag in sendmsg() Björn Töpel
2020-11-25  7:16   ` Magnus Karlsson
2020-11-19  8:30 ` [PATCH bpf-next v3 05/10] xsk: add busy-poll support for {recv,send}msg() Björn Töpel
2020-11-25  7:58   ` Magnus Karlsson
2020-11-19  8:30 ` [PATCH bpf-next v3 06/10] xsk: propagate napi_id to XDP socket Rx path Björn Töpel
2020-11-25 14:47   ` Magnus Karlsson
2020-11-25 21:14   ` Michael S. Tsirkin
2021-09-29 18:33   ` kernel test robot
2021-09-30  6:04     ` Magnus Karlsson
2021-10-02  2:07       ` [kbuild-all] " Philip Li
2021-11-05 20:17   ` kernel test robot
2020-11-19  8:30 ` [PATCH bpf-next v3 07/10] samples/bpf: use recvfrom() in xdpsock/rxdrop Björn Töpel
2020-11-25  7:59   ` Magnus Karlsson
2020-11-19  8:30 ` [PATCH bpf-next v3 08/10] samples/bpf: use recvfrom() in xdpsock/l2fwd Björn Töpel
2020-11-25  8:00   ` Magnus Karlsson
2020-11-19  8:30 ` [PATCH bpf-next v3 09/10] samples/bpf: add busy-poll support to xdpsock Björn Töpel
2020-11-25  8:19   ` Magnus Karlsson
2020-11-19  8:30 ` [PATCH bpf-next v3 10/10] samples/bpf: add option to set the busy-poll budget Björn Töpel
2020-11-25  8:23   ` Magnus Karlsson
2020-11-23 13:31 ` [PATCH bpf-next v3 00/10] Introduce preferred busy-polling Björn Töpel
2020-11-23 23:54   ` Jakub Kicinski
2020-11-24  0:14 ` Jakub Kicinski

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