netdev - Re: [PATCH net-next 2/2] net/mlx5e: Query minimum required header copy during xmit

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Message-Id: <20160721.091514.851679663543797906.davem@davemloft.net>
Date:	Thu, 21 Jul 2016 09:15:14 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	saeedm@....mellanox.co.il
Cc:	alexei.starovoitov@...il.com, saeedm@...lanox.com,
	netdev@...r.kernel.org, ogerlitz@...lanox.com, hadarh@...lanox.com
Subject: Re: [PATCH net-next 2/2] net/mlx5e: Query minimum required header
 copy during xmit

From: Saeed Mahameed <saeedm@....mellanox.co.il>
Date: Thu, 21 Jul 2016 11:22:32 +0300

> On Thu, Jul 21, 2016 at 8:15 AM, Alexei Starovoitov
> <alexei.starovoitov@...il.com> wrote:
>> On Thu, Jul 21, 2016 at 01:20:02AM +0300, Saeed Mahameed wrote:
>>> From: Hadar Hen Zion <hadarh@...lanox.com>
>>>
>>> Add support for query the minimum inline mode from the Firmware.
>>> It is required for correct TX steering according to L3/L4 packet
>>> headers.
>>>
>>> Each send queue (SQ) has inline mode that defines the minimal required
>>> headers that needs to be copied into the SQ WQE.
>>> The driver asks the Firmware for the wqe_inline_mode device capability
>>> value.  In case the device capability defined as "vport context" the
>>> driver must check the reported min inline mode from the vport context
>>> before creating its SQs.
>>>
>>> Signed-off-by: Hadar Hen Zion <hadarh@...lanox.com>
>>> Signed-off-by: Saeed Mahameed <saeedm@...lanox.com>
>> ...
>>> +     int outlen = MLX5_ST_SZ_BYTES(query_nic_vport_context_out);
>>> +     u32 *out;
>>> +
>>> +     out = mlx5_vzalloc(outlen);
>>> +     if (!out)
>>> +             return;
>>
>> Just discovered this...
>> outlen is a small constant here, yet you want to try to vmalloc it?
>> What is the point?
>> There are 67 places in mlx5 where failed kmalloc is retried with
>> vmalloc... was that path ever tested?
> 
> The point is that there are a lot of places in the code that want to
> allocate huge commands and mlx5_vzalloc is a nice black box that
> provides the method to allocate such huge chunks of memory.

If it's a "black box" then don't mention that it uses vmalloc in the
function name.