linux-kernel - Re: [PATCH V2] mlx4_core: allocate ICM memory in page size chunks

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Message-ID: <f71278c2-a111-1bf6-2ff3-d9a8dd46bfbe@gmail.com>
Date:   Tue, 15 May 2018 12:08:01 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Qing Huang <qing.huang@...cle.com>,
        Tariq Toukan <tariqt@...lanox.com>, davem@...emloft.net,
        haakon.bugge@...cle.com, yanjun.zhu@...cle.com
Cc:     netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] mlx4_core: allocate ICM memory in page size chunks



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.