From: Sowmini Varadhan <sowmini.varadhan@oracle.com>
To: David Miller <davem@davemloft.net>
Cc: raghuram.kothakota@oracle.com, netdev@vger.kernel.org
Subject: Re: [PATCH net-next 2/2] sunvnet: Re-check for a VIO_DESC_READY data descriptor after short udelay()
Date: Tue, 02 Sep 2014 06:27:54 -0400 [thread overview]
Message-ID: <54059BAA.1080307@oracle.com> (raw)
In-Reply-To: <20140901.204715.2121922580015092507.davem@davemloft.net>
On 09/01/2014 11:47 PM, David Miller wrote:
>
> If there were no more packets coming, this is wasted useless polling
> time in atomic context.
turns out that this gives a 20-30% perf improvement for tests like
iperf.
when there are no more packets coming, the extra 12 microsecond
delay is not that big of a deal anyway. The point was that the extra
12 micro-second tax in the quiescent network state is less expensive
than exiting interrupt context, taking another interrupt and doing
another ldc_read, when there is actually a burst of packets.
notice that there are many other such udelay() loops elsewhere in
the code.
I can remove the retries and submit patch 1/1 again later today.
>
> Everything should be event based, and we should not be compensating
> and making sacrifices for a producer slower than we are as a consumer.
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next prev parent reply other threads:[~2014-09-02 10:27 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-29 20:18 [PATCH net-next 2/2] sunvnet: Re-check for a VIO_DESC_READY data descriptor after short udelay() Sowmini Varadhan
2014-09-02 3:47 ` David Miller
2014-09-02 10:27 ` Sowmini Varadhan [this message]
2014-09-02 16:43 ` Raghuram Kothakota
2014-09-02 16:56 ` Sowmini Varadhan
2014-09-02 17:33 ` Raghuram Kothakota
2014-09-02 20:59 ` David Miller
2014-09-03 17:12 ` Sowmini Varadhan
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