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From: Stephen Hemminger <stephen@networkplumber.org>
To: Ciara Loftus <ciara.loftus@intel.com>
Cc: dev@dpdk.org, xiaolong.ye@intel.com, magnus.karlsson@intel.com
Subject: Re: [dpdk-dev] [PATCH] net/af_xdp: optimisations to improve packet loss
Date: Tue, 16 Jun 2020 20:42:16 -0700
Message-ID: <20200616204216.35e362b3@hermes.lan> (raw)
In-Reply-To: <20200612141746.9450-1-ciara.loftus@intel.com>

On Fri, 12 Jun 2020 14:17:46 +0000
Ciara Loftus <ciara.loftus@intel.com> wrote:

> This commit makes some changes to the AF_XDP PMD in an effort to improve
> its packet loss characteristics.
> 
> 1. In the case of failed transmission due to inability to reserve a tx
> descriptor, the PMD now pulls from the completion ring, issues a syscall
> in which the kernel attempts to complete outstanding tx operations, then
> tries to reserve the tx descriptor again. Prior to this we dropped the
> packet after the syscall and didn't try to re-reserve.
> 
> 2. During completion ring cleanup, always pull as many entries as possible
> from the ring as opposed to the batch size or just how many packets
> we're going to attempt to send. Keeping the completion ring emptier should
> reduce failed transmissions in the kernel, as the kernel requires space in
> the completion ring to successfully tx.
> 
> 3. Size the fill ring as twice the receive ring size which may help reduce
> allocation failures in the driver.
> 
> With these changes, a benchmark which measured the packet rate at which
> 0.01% packet loss could be reached improved from ~0.1G to ~3Gbps.
> 
> Signed-off-by: Ciara Loftus <ciara.loftus@intel.com>

You might want to add the ability to emulate a tx_free threshold
by pulling more completions earlier.

  parent reply	other threads:[~2020-06-17  3:42 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-12 14:17 Ciara Loftus
2020-06-17  2:34 ` Ye Xiaolong
2020-06-17  3:42 ` Stephen Hemminger [this message]
2020-06-23 14:50   ` Loftus, Ciara

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