netdev - Re: Page allocator order-0 optimizations merged

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Message-ID: <26c4d7a4-c8a7-fbad-d2be-a5a90f6d93d3@gmail.com>
Date:   Tue, 28 Mar 2017 19:05:12 +0300
From:   Tariq Toukan <ttoukan.linux@...il.com>
To:     Mel Gorman <mgorman@...hsingularity.net>,
        Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     Pankaj Gupta <pagupta@...hat.com>,
        Tariq Toukan <tariqt@...lanox.com>, netdev@...r.kernel.org,
        akpm@...ux-foundation.org, linux-mm <linux-mm@...ck.org>,
        Saeed Mahameed <saeedm@...lanox.com>
Subject: Re: Page allocator order-0 optimizations merged



On 28/03/2017 10:32 AM, Tariq Toukan wrote:
>
>
> On 27/03/2017 4:32 PM, Mel Gorman wrote:
>> On Mon, Mar 27, 2017 at 02:39:47PM +0200, Jesper Dangaard Brouer wrote:
>>> On Mon, 27 Mar 2017 10:55:14 +0200
>>> Jesper Dangaard Brouer <brouer@...hat.com> wrote:
>>>
>>>> A possible solution, would be use the local_bh_{disable,enable} instead
>>>> of the {preempt_disable,enable} calls.  But it is slower, using numbers
>>>> from [1] (19 vs 11 cycles), thus the expected cycles saving is
>>>> 38-19=19.
>>>>
>>>> The problematic part of using local_bh_enable is that this adds a
>>>> softirq/bottom-halves rescheduling point (as it checks for pending
>>>> BHs).  Thus, this might affects real workloads.
>>>
>>> I implemented this solution in patch below... and tested it on mlx5 at
>>> 50G with manually disabled driver-page-recycling.  It works for me.
>>>
>>> To Mel, that do you prefer... a partial-revert or something like this?
>>>
>>
>> If Tariq confirms it works for him as well, this looks far safer patch
>
> Great.
> I will test Jesper's patch today in the afternoon.
>

It looks very good!
I get line-rate (94Gbits/sec) with 8 streams, in comparison to less than 
55Gbits/sec before.

Many thanks guys.

>> than having a dedicate IRQ-safe queue. Your concern about the BH
>> scheduling point is valid but if it's proven to be a problem, there is
>> still the option of a partial revert.
>>