From: Giuseppe CAVALLARO <peppe.cavallaro@st•com>
To: David Laight <David.Laight@ACULAB•COM>,
"netdev@vger•kernel.org" <netdev@vger•kernel.org>
Subject: Re: [PATCH (net.git) 2/4] stmmac: fix and better tune the default buffer sizes
Date: Thu, 27 Feb 2014 14:03:00 +0100 [thread overview]
Message-ID: <530F3784.5050304@st.com> (raw)
In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6D0F6CC945@AcuExch.aculab.com>
On 2/27/2014 11:51 AM, David Laight wrote:
> From: Giuseppe Cavallaro
>> This patch is to fix and tune the default buffer sizes.
>> It reduces the default bufsize used by the driver from
>> 2048 to 1518 (taking into account the extra 4 bytes in case of VLAN).
> ...
>> -#define DMA_BUFFER_SIZE BUF_SIZE_4KiB
>> -static int buf_sz = DMA_BUFFER_SIZE;
>
> Does this means that the old default was 4k, not the 2k in the
> patch description.
no pbl, I'll fix it in the patch subject.
>
>> +#ifdef STMMAC_VLAN_TAG_USED
>> +#define DEFAULT_BUFSIZE (VLAN_ETH_FRAME_LEN + ETH_FCS_LEN)
>> +#else
>> +#define DEFAULT_BUFSIZE (ETH_FRAME_LEN + ETH_FCS_LEN)
>> +#endif
> ...
>> + if (unlikely((buf_sz < DEFAULT_BUFSIZE) || (buf_sz > BUF_SIZE_16KiB)))
>> + buf_sz = DEFAULT_BUFSIZE;
>
> It doesn't seem right to me for the minimum buffer size to
> depend on a compile-time option for VLAN.
Hmm, I can have a default suitable for all the cases.
Indeed other drivers program buffers (dlink/sundance.c)
and do other settings according Koption like CONFIG_VLAN_8021Q.
It is not a problem to review and delete it.
> Also (provided the hardware supports it) the rx buffers (are these
> the ones being sized?) need to be aligned on a 4n+2 boundary in
> order to avoid a realignment copy later on.
This is true and indeed I had added the STMMAC_ALIGN to align all.
In the past to get the right alignment for SH4.
> So I'm not sure that some of these sizes are right and/or optimal.
What do you suggest?
Maybe, I can use a default for sure < 4KiB suitable to be used for VLAN
frames (it will be aligned later).
Peppe
>
> David
>
>
>
>
>
next prev parent reply other threads:[~2014-02-27 13:03 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-27 10:35 [PATCH (net.git) 0/4 (v3)] stmmac fixes: EEE and chained mode Giuseppe Cavallaro
2014-02-27 10:35 ` [PATCH (net.git) 1/4] stmmac: disable at run-time the EEE if not supported Giuseppe Cavallaro
2014-02-27 10:35 ` [PATCH (net.git) 2/4] stmmac: fix and better tune the default buffer sizes Giuseppe Cavallaro
2014-02-27 10:51 ` David Laight
2014-02-27 13:03 ` Giuseppe CAVALLARO [this message]
2014-02-27 13:31 ` David Laight
2014-02-27 13:54 ` Giuseppe CAVALLARO
2014-03-04 7:20 ` Giuseppe CAVALLARO
2014-03-05 9:33 ` David Laight
2014-03-05 10:26 ` Giuseppe CAVALLARO
2014-02-27 13:34 ` Giuseppe CAVALLARO
2014-02-27 10:35 ` [PATCH (net.git) 3/4] stmmac: dwmac-sti: fix broken STiD127 compatibility Giuseppe Cavallaro
2014-02-27 10:35 ` [PATCH (net.git) 4/4] stmmac: fix chained mode Giuseppe Cavallaro
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