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Message-ID: <0873b65b-2217-005d-0b42-4af6ad66cc0f@gmail.com>
Date: Tue, 28 Mar 2017 10:32:19 +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 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.
> 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.
>
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