Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH V2] mlx4_core: allocate ICM memory in page size chunks
To:     Qing Huang <qing.huang@oracle.com>,
        Tariq Toukan <tariqt@mellanox.com>, davem@davemloft.net,
        haakon.bugge@oracle.com, yanjun.zhu@oracle.com
Cc:     netdev@vger.kernel.org, linux-rdma@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20180511192318.22342-1-qing.huang@oracle.com>
 <2797ac27-022c-0818-388c-e4a6131ad1ca@gmail.com>
 <ff9c44ca-eaae-cb3e-4c69-e9e3cbb72ca1@oracle.com>
 <1ded7d49-0ba2-3594-f840-74d7cf37a0eb@mellanox.com>
 <f4c5d8d3-1eea-8566-9921-a9dc48435f66@oracle.com>
From:   Eric Dumazet <eric.dumazet@gmail.com>
Message-ID: <f71278c2-a111-1bf6-2ff3-d9a8dd46bfbe@gmail.com>
Date:   Tue, 15 May 2018 12:08:01 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.6.0
MIME-Version: 1.0
In-Reply-To: <f4c5d8d3-1eea-8566-9921-a9dc48435f66@oracle.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 05/15/2018 11:53 AM, Qing Huang wrote:
> 
>> This is control path so it is less latency-sensitive.
>> Let's not produce unnecessary degradation here, please call kvzalloc so we maintain a similar behavior when contiguous memory is available, and a fallback for resiliency.
> 
> No sure what exactly degradation is caused by vzalloc here. I think it's better to keep physically contiguous pages
> to other requests which really need them. Besides slow path/mem compacting can be really expensive.
>

Just use kvzalloc(), and you get the benefit of having contiguous memory if available,
without expensive compact phase.

This thing _automatically_ falls back to vmalloc(), thus your problem will be solved.

If you are not sure, trust others.