linux-kernel - Re: [PATCH] mwifiex: add __GFP

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Message-ID: <CABicQ-UJ1kniq6m86QcyVZBPznvNexfrUrTk3A_=GmZy69hvCA@mail.gmail.com>
Date:	Tue, 29 Mar 2016 17:27:16 +0800
From:	Wei-Ning Huang <wnhuang@...gle.com>
To:	Kalle Valo <kvalo@...eaurora.org>
Cc:	Linux Wireless <linux-wireless@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Amitkumar Karwar <akarwar@...vell.com>,
	Nishant Sarmukadam <nishants@...vell.com>,
	Sameer Nanda <snanda@...gle.com>, 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

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

On Tue, Mar 29, 2016 at 4:37 PM, Kalle Valo <kvalo@...eaurora.org> wrote:
> Wei-Ning Huang <wnhuang@...omium.org> writes:
>
>> "single skb allocation failure" happens when system is under heavy
>> memory pressure.  Add __GFP_REPEAT to skb allocation call so kernel
>> attempts to reclaim pages and retry the allocation.
>>
>> Signed-off-by: Wei-Ning Huang <wnhuang@...omium.org>
>
> Is this really a proper way to fix the issue? This is the first time I'm
> hearing about the flag and there isn't even a single user in
> drivers/net. I would like to get confirmation from others that
> __GFP_REPEAT is really ok to use in a wireless driver before I can take
> this.
>
> --
> Kalle Valo

-- 
Wei-Ning Huang, 黃偉寧 | Software Engineer, Google Inc., Taiwan |
wnhuang@...gle.com | Cell: +886 910-380678