linux-kernel - Re: [PATCH] Improve Atheros ethernet driver not to do order 4 GFP

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Message-Id: <20151201.153628.148150792813486828.davem@davemloft.net>
Date:	Tue, 01 Dec 2015 15:36:28 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	pavel@....cz, mhocko@...nel.org, akpm@...l.org,
	linux-kernel@...r.kernel.org, jcliburn@...il.com,
	chris.snook@...il.com, netdev@...r.kernel.org, rjw@...ysocki.net,
	linux-mm@...ck.org, nic-devel@...lcomm.com, ronangeles@...il.com,
	ebiederm@...ssion.com
Subject: Re: [PATCH] Improve Atheros ethernet driver not to do order 4
 GFP_ATOMIC allocation

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Mon, 30 Nov 2015 09:58:23 -0800

> On Sat, 2015-11-28 at 15:51 +0100, Pavel Machek wrote:
>> atl1c driver is doing order-4 allocation with GFP_ATOMIC
>> priority. That often breaks  networking after resume. Switch to
>> GFP_KERNEL. Still not ideal, but should be significantly better.
>>     
>> Signed-off-by: Pavel Machek <pavel@....cz>
>> 
>> diff --git a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
>> index 2795d6d..afb71e0 100644
>> --- a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
>> +++ b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
>> @@ -1016,10 +1016,10 @@ static int atl1c_setup_ring_resources(struct atl1c_adapter *adapter)
>>  		sizeof(struct atl1c_recv_ret_status) * rx_desc_count +
>>  		8 * 4;
>>  
>> -	ring_header->desc = pci_alloc_consistent(pdev, ring_header->size,
>> -				&ring_header->dma);
>> +	ring_header->desc = dma_alloc_coherent(&pdev->dev, ring_header->size,
>> +					       &ring_header->dma, GFP_KERNEL);
>>  	if (unlikely(!ring_header->desc)) {
>> -		dev_err(&pdev->dev, "pci_alloc_consistend failed\n");
>> +		dev_err(&pdev->dev, "could not get memmory for DMA buffer\n");
>>  		goto err_nomem;
>>  	}
>>  	memset(ring_header->desc, 0, ring_header->size);
>> 
> 
> It seems there is a missed opportunity to get rid of the memset() here,
> by adding __GFP_ZERO to the dma_alloc_coherent() GFP_KERNEL mask,
> or simply using dma_zalloc_coherent()

Also, the Subject line needs to be adjusted.  The proper format for
the Subject line is:

	[PATCH $TREE] $subsystem: $description.

Where "$TREE" is either 'net' or 'net-next', $subsystem is the lowercase
name of the driver (here 'atl1c') and then a colon, and then a space, and
then the single-line description.

Thanks.
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