From: Paul Gortmaker <penguin@muskoka.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Jeff Garzik <jgarzik@pobox.com>
Subject: Re: [PATCH] 2.6.9 Use skb_padto() in drivers/net/8390.c
Date: Sun, 09 Jan 2005 21:41:44 -0500 [thread overview]
Message-ID: <41E1EB68.5000709@muskoka.com> (raw)
In-Reply-To: <1105197689.10505.22.camel@localhost.localdomain>
Alan Cox wrote:
>On Sad, 2005-01-08 at 08:33, Paul Gortmaker wrote:
>
>
>>Is it possible that skb_padto has since got its act together? Reason I
>>ask is that I just dusted off a crusty 386dx40 (doesn't get much older
>>
>
>Could be - kmalloc has probably improved but the skbuffs have got far
>more complex
>
>
>>than that) with a wd8013. As a basic test, I did ttcp Tx tests with small
>>packets and they came out to all intents and purposes, identical. Kernel
>>was 2.6.10, with stack vs skb_padto, each size test ran 3 times, even tested
>>packets bigger than ETH_ZLEN as a (hopefully) invariant. I've attached the
>>edited down results below.
>>
>
>What are you testing ? I don't see the relationship between network
>throughput and efficiency on this device.
I was thinking that for a sufficiently slow CPU running at 100% (hence the
lowly 386), the throughput would be influenced by how efficiently we can
get in, get the Tx set up and get out.
>Drop it on a pentium or late 486 and use the tsc to compare the two code
>paths. One is much much more efficienct.
Using rdtscl over the area affected by the patch on the two variants for a
sample of 234 small packets, I see an average of 4141 for using the
existing stack scratch area, and 4162 for using skb_padto. That is a
difference of about 0.5%, which is significantly less than the typical
spread in the samples themselves. To help give a relevant scale, feeding
it a larger 1400 byte packet comes in at around 60,000 cycles on this
particular box. Am I being optimistic to see this as good news -- meaning
that there is no longer a need for driver specific padto implementations,
whereas it looks like there was back when you did your tests?
Paul.
next prev parent reply other threads:[~2005-01-10 2:50 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <41DED9FA.7080106@pobox.com>
2005-01-08 8:33 ` [PATCH] 2.6.9 Use skb_padto() in drivers/net/8390.c] Paul Gortmaker
2005-01-08 15:45 ` Alan Cox
2005-01-10 2:41 ` Paul Gortmaker [this message]
2005-01-10 18:28 ` [PATCH] 2.6.9 Use skb_padto() in drivers/net/8390.c Alan Cox
2005-02-19 5:20 ` Jeff Garzik
2005-02-19 14:06 ` Alan Cox
[not found] <200501070309.j0739IG6007753@hera.kernel.org>
2005-01-07 15:46 ` Alan Cox
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