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From: Jimmy PERCHET <jimmy.perchet@parrot•com>
To: Giuseppe CAVALLARO <peppe.cavallaro@st•com>
Cc: <netdev@vger•kernel.org>, Jimmy Perchet <jimmy.perchet@parrot•com>
Subject: Re: [PATCH RFC 0/5] net:stmmac: fix jumbo frames handling and optimisation
Date: Fri, 18 Oct 2013 18:24:04 +0200	[thread overview]
Message-ID: <526160A4.7030507@parrot.com> (raw)
In-Reply-To: <525EF8FF.2010206@st.com>

Hello Peppe,

Thanks for your concern,

I add some details :

> I tested jumbo on chips w/o enhanced some time ago, so welcome further
> tests as you did (maybe on new chips).

I'm working with 3.71a version, in 2KiB + 2KiB configuration.

>> *(1/5) Threshold dma mode is needed on rx path if jumbo frames are expected.
> 
> hmm, this depends on the HW. In the past I used HW with a Fifo that is
> 16KiB for rx buffers and 8KiB for tx.

I used rxfifo_over_2048 flag in order to guess if threshold mode is necessary.


>> *(3/5) On low speed link (10MBit/s), some TX descriptors can remain dirty
>> if the tx coalescence timer expires before they were treated. Re-arm timer
>> in this case.
> 
> hmm not clear to me, let me look at the patch. I hope the link should
> not impact... never seen on my side.
> 
Tx coalescence default parameters are : one interrupt every 64 descriptors
and 40ms timer.
Let say, one is transferring 63 jumbo frames(9KiB) over 10Mb/s link:
* 63<64 there is no interrupt.
* when the timer expires, only 5 descriptors have to be cleaned.(40ms@10Mb/s)
* at the end, 58 dirty descriptors remain.
Normally, they will be cleaned at the next transfer. The real problem appears
if the socket's "wmem" is too small. The transfer stall :
*Socket is waiting for buffer's cleanup before performing a new transfer.
*Driver is waiting for new transfer before performing cleanup.
Re-arming the timer allows to continue cleanup, thus the socket's
wake-up threshold will be reach.


Best Regards,
Jimmy

     prev parent reply	other threads:[~2013-10-18 16:24 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-10-16 15:24 [PATCH RFC 0/5] net:stmmac: fix jumbo frames handling and optimisation Jimmy Perchet
2013-10-16 15:24 ` [PATCH RFC 1/5] net:stmmac: set threshold/store and forward mode according to mtu size Jimmy Perchet
2013-10-21  8:47   ` Giuseppe CAVALLARO
2013-10-21  9:58     ` Rayagond K
2013-10-21 13:49       ` Giuseppe CAVALLARO
2013-10-16 15:24 ` [PATCH RFC 2/5] net:stmmac: fix rx buffer allocation Jimmy Perchet
2013-10-21  8:54   ` Giuseppe CAVALLARO
2013-10-16 15:24 ` [PATCH RFC 3/5] net:stmmac: ensure we reclaim all dirty descriptors Jimmy Perchet
2013-10-16 17:46   ` Sergei Shtylyov
2013-10-18  8:32     ` Jimmy PERCHET
2013-10-21  9:07   ` Giuseppe CAVALLARO
2013-10-21 13:10     ` Jimmy PERCHET
2013-10-21 18:32       ` Eric Dumazet
2013-10-21 18:49         ` Eric Dumazet
2013-10-22 13:33           ` Giuseppe CAVALLARO
2013-10-16 15:24 ` [PATCH RFC 4/5] net:stmmac: fix jumbo frame handling Jimmy Perchet
2013-10-21 13:40   ` Giuseppe CAVALLARO
2013-10-21 16:28     ` Jimmy PERCHET
2013-10-22 13:24       ` Giuseppe CAVALLARO
2013-10-16 15:24 ` [PATCH RFC 5/5] net:stmmac: asynchronous tx_clean Jimmy Perchet
2013-10-21 13:52   ` Giuseppe CAVALLARO
2013-10-21 16:30     ` Eric Dumazet
2013-10-21 18:05       ` Jimmy PERCHET
2013-10-21 18:24         ` Eric Dumazet
2013-10-16 20:37 ` [PATCH RFC 0/5] net:stmmac: fix jumbo frames handling and optimisation Giuseppe CAVALLARO
2013-10-18 16:24   ` Jimmy PERCHET [this message]

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