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[PATCH] mwifiex: add __GFP_REPEAT to skb allocation call

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  [PATCH] mwifiex: add __GFP_REPEAT to skb allocation call Wei-Ning Huang <wnhuang@chromium.org> - 2016-03-29 06:50 +0200
    Re: [PATCH] mwifiex: add __GFP_REPEAT to skb allocation call James Cameron <quozl@laptop.org> - 2016-03-29 07:40 +0200
    Re: [PATCH] mwifiex: add __GFP_REPEAT to skb allocation call Kalle Valo <kvalo@codeaurora.org> - 2016-03-29 10:40 +0200
      Re: [PATCH] mwifiex: add __GFP_REPEAT to skb allocation call Wei-Ning Huang <wnhuang@google.com> - 2016-03-29 11:30 +0200
        RE: [PATCH] mwifiex: add __GFP_REPEAT to skb allocation call Amitkumar Karwar <akarwar@marvell.com> - 2016-03-29 13:00 +0200
        Re: [PATCH] mwifiex: add __GFP_REPEAT to skb allocation call Eric Dumazet <eric.dumazet@gmail.com> - 2016-03-29 15:00 +0200

#1365848 — [PATCH] mwifiex: add __GFP_REPEAT to skb allocation call

"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@chromium.org>
---
 drivers/net/wireless/marvell/mwifiex/sdio.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/marvell/mwifiex/sdio.c b/drivers/net/wireless/marvell/mwifiex/sdio.c
index b2c839a..c64989c 100644
--- a/drivers/net/wireless/marvell/mwifiex/sdio.c
+++ b/drivers/net/wireless/marvell/mwifiex/sdio.c
@@ -1124,7 +1124,8 @@ static void mwifiex_deaggr_sdio_pkt(struct mwifiex_adapter *adapter,
 			break;
 		}
 		skb_deaggr = mwifiex_alloc_dma_align_buf(pkt_len,
-							 GFP_KERNEL | GFP_DMA);
+							 GFP_KERNEL | GFP_DMA |
+							 __GFP_REPEAT);
 		if (!skb_deaggr)
 			break;
 		skb_put(skb_deaggr, pkt_len);
@@ -1374,7 +1375,8 @@ static int mwifiex_sdio_card_to_host_mp_aggr(struct mwifiex_adapter *adapter,
 			/* copy pkt to deaggr buf */
 			skb_deaggr = mwifiex_alloc_dma_align_buf(len_arr[pind],
 								 GFP_KERNEL |
-								 GFP_DMA);
+								 GFP_DMA |
+								 __GFP_REPEAT);
 			if (!skb_deaggr) {
 				mwifiex_dbg(adapter, ERROR, "skb allocation failure\t"
 					    "drop pkt len=%d type=%d\n",
@@ -1416,7 +1418,8 @@ rx_curr_single:
 		mwifiex_dbg(adapter, INFO, "info: RX: port: %d, rx_len: %d\n",
 			    port, rx_len);
 
-		skb = mwifiex_alloc_dma_align_buf(rx_len, GFP_KERNEL | GFP_DMA);
+		skb = mwifiex_alloc_dma_align_buf(rx_len, GFP_KERNEL | GFP_DMA |
+						  __GFP_REPEAT);
 		if (!skb) {
 			mwifiex_dbg(adapter, ERROR,
 				    "single skb allocated fail,\t"
@@ -1521,7 +1524,8 @@ static int mwifiex_process_int_status(struct mwifiex_adapter *adapter)
 		rx_len = (u16) (rx_blocks * MWIFIEX_SDIO_BLOCK_SIZE);
 		mwifiex_dbg(adapter, INFO, "info: rx_len = %d\n", rx_len);
 
-		skb = mwifiex_alloc_dma_align_buf(rx_len, GFP_KERNEL | GFP_DMA);
+		skb = mwifiex_alloc_dma_align_buf(rx_len, GFP_KERNEL | GFP_DMA |
+						  __GFP_REPEAT);
 		if (!skb)
 			return -1;
 
-- 
2.8.0.rc3.226.g39d4020

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#1365865

On Tue, Mar 29, 2016 at 12:47:20PM +0800, Wei-Ning Huang wrote:
> "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.

Oh, that's interesting, we're back to this symptom again.

Nice to see this fix.

Heavy memory pressure on 3.5 caused dev_alloc_skb failure in this
driver.  Tracked at OLPC as #12694.

-- 
James Cameron
http://quozl.netrek.org/

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#1366007

Wei-Ning Huang <wnhuang@chromium.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@chromium.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

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#1366057

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@marvell 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@codeaurora.org> wrote:
> Wei-Ning Huang <wnhuang@chromium.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@chromium.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@google.com | Cell: +886 910-380678

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#1366159

> From: Wei-Ning Huang [mailto:wnhuang@google.com]
> Sent: Tuesday, March 29, 2016 2:57 PM
> To: Kalle Valo
> Cc: Linux Wireless; LKML; Amitkumar Karwar; Nishant Sarmukadam; Sameer
> Nanda; netdev@vger.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@marvell 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

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#1366247

On Tue, 2016-03-29 at 17:27 +0800, Wei-Ning Huang wrote:
> 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@marvell 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.

Before SG is implemented, you really need to copy incoming frames into
smallest chunks (to get lowest skb->truesize) and leave the 64KB
allocated stuff forever in the driver.

__GFP_REPEAT wont really solve the issue.

It seems the problem comes from the fact that the drivers calls
dev_kfree_skb_any() after calling mwifiex_deaggr_sdio_pkt(), instead of
recycling this very precious 64KB skb once memory gets fragmented.

Another problem is that mwifiex_deaggr_sdio_pkt() uses
mwifiex_alloc_dma_align_buf() with GFP_KERNEL | GFP_DMA

Really GFP_DMA makes no sense here, since the skb is going to be
processed by the stack, which has no such requirement.

Please use normal skb allocations there.

diff --git a/drivers/net/wireless/marvell/mwifiex/sdio.c b/drivers/net/wireless/marvell/mwifiex/sdio.c
index b2c839a..8404db5 100644
--- a/drivers/net/wireless/marvell/mwifiex/sdio.c
+++ b/drivers/net/wireless/marvell/mwifiex/sdio.c
@@ -1123,8 +1123,8 @@ static void mwifiex_deaggr_sdio_pkt(struct mwifiex_adapter *adapter,
 				    __func__, pkt_len, blk_size);
 			break;
 		}
-		skb_deaggr = mwifiex_alloc_dma_align_buf(pkt_len,
-							 GFP_KERNEL | GFP_DMA);
+		skb_deaggr = __netdev_alloc_skb_ip_align(NULL, pkt_len,
+							 GFP_KERNEL);
 		if (!skb_deaggr)
 			break;
 		skb_put(skb_deaggr, pkt_len);

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