netdev - RE: [PATCH] mwifiex: add __GFP_REPEAT to skb allocation call

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Date:	Tue, 29 Mar 2016 10:51:50 +0000
From:	Amitkumar Karwar <akarwar@...vell.com>
To:	Wei-Ning Huang <wnhuang@...gle.com>,
	Kalle Valo <kvalo@...eaurora.org>
CC:	Linux Wireless <linux-wireless@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Nishant Sarmukadam <nishants@...vell.com>,
	Sameer Nanda <snanda@...gle.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Sonny Rao <sonnyrao@...omium.org>,
	Douglas Anderson <dianders@...omium.org>
Subject: RE: [PATCH] mwifiex: add __GFP_REPEAT to skb allocation call

> From: Wei-Ning Huang [mailto:wnhuang@...gle.com]
> Sent: Tuesday, March 29, 2016 2:57 PM
> To: Kalle Valo
> Cc: Linux Wireless; LKML; Amitkumar Karwar; Nishant Sarmukadam; Sameer
> Nanda; netdev@...r.kernel.org; Sonny Rao; Douglas Anderson
> Subject: Re: [PATCH] mwifiex: add __GFP_REPEAT to skb allocation call
> 
> Adding some chromium devs to the thread.
> 
> In, http://lxr.free-electrons.com/source/mm/page_alloc.c#L3152
> 
> The default mm retry allocation when 'order <= PAGE_ALLOC_COSTLY_ORDER'
> of gfp_mask contains __GFP_REPEAT.
> PAGE_ALLOC_COSTLY_ORDER is defined to be 3. On systems with page size =
> 4K, this means memory compaction and retry is only done when the size of
> allocation is <= 32K In mwifiex, the allocation size is 64K. When we
> have system with memory fragmentation and allocation failed, there will
> be no retry.
> This is why we need to add __GFP_REPEAT here to allow the system to
> perform memory compaction and retry allocation.
> 
> Maybe Amit@...vell can comment on if this is a good fix on this issue.
> I'm also aware that marvell is the progress of implementing
> scatter/gatter for mwifiex, which can also fix the issue.
> 
> Wei-Ning
> 

This fix would be useful. We have a feature called single port aggregation in which sometimes data received from SDIO interface can be >32k (but less than 64k). This feature improves throughput performance. We are preparing patches for scatter/gather feature. but scatter/gather won't be supported by some platforms. Hence this fix would still be needed.

Regards,
Amitkumar