[PATCH 2/6] sfxge: limit software Tx queue size

[Andrew Rybchenko]

Gleb,

On 03/18/2014 05:24 PM, Gleb Smirnoff wrote:
>    Andrew,
>
> On Tue, Mar 18, 2014 at 01:55:01PM +0400, Andrew Rybchenko wrote:
> A> sfxge: limit software Tx queue size
> A>
> A> Previous implementation limits put queue size only (when Tx lock can't
> A> be acquired),
> A> but get queue may grow unboundedly which results in mbuf pools
> A> exhaustion and
> A> latency growth.
> A>
> A> Submitted-by:   Andrew Rybchenko <Andrew.Rybchenko at oktetlabs.ru>
> A> Sponsored by:   Solarflare Communications, Inc.
>
> The interaction between sfxge_tx_qdpl_put() and sfxge_tx_packet_add()
> is quite complex and I couldn't resist from suggesting you to
> simplify the code.
>
> Can you please look into attached patch?
>
> - Inline sfxge_tx_qdpl_put() into sfxge_tx_packet_add().
> - Simplify the 'locked' logic.
> - Add your PATCH 1/6, the mbuf leak fix.
> - Add your PATCH 2/6, the SFXGE_TX_DPL_GET_PKT_LIMIT_DEFAULT check.
I don't like "locked" flag passed to qdpl_put() function as well.
However, I prefer to keep patches granular and avoid mixing of different 
changes in single patch. If the initial patch is OK, please, submit it 
to repository. Then, I'll rebase your patch, discuss it locally and come 
back to you.

BTW, I see that many drivers use drbr for software Tx queue. What do you 
think, would it be beneficial to use it instead of the list implemented 
here?

Please, find initial patch with few minor fixes (TAB after #define and 
@->" at " in suggested commit message) attached.

Thanks a lot,
Andrew.

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