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PostPosted: Tue Jan 27, 2009 1:34 am 
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Ever since upgrading my Linkstation Live v2 to the newer armel kernels (davy_gravy's 2.6.27.4 and a self-compiled 2.6.28.1), I've been seeing TONS of "page allocation failure" messages in my syslog, similar to the following:
Code:
Jan 25 11:17:15 LS1 kernel: swapper: page allocation failure. order:2, mode:0x20
Jan 25 11:17:15 LS1 kernel: [<c00305b8>] (dump_stack+0x0/0x14) from [<c0079dd0>(__alloc_pages_internal+0x30c/0x3f8)
Jan 25 11:17:15 LS1 kernel: [<c0079ac4>] (__alloc_pages_internal+0x0/0x3f8) from [<c00985a8>] (cache_alloc_refill+0x34c/0x668)
Jan 25 11:17:15 LS1 kernel: [<c009825c>] (cache_alloc_refill+0x0/0x668) from [<c00989a0>] (__kmalloc+0xdc/0xe8)
Jan 25 11:17:15 LS1 kernel: [<c00988c4>] (__kmalloc+0x0/0xe8) from [<c02e43b8>] (__alloc_skb+0x54/0xf8)
Jan 25 11:17:15 LS1 kernel:  r7:c7807c20 r6:00002380 r5:00000020 r4:c13cf780
Jan 25 11:17:15 LS1 kernel: [<c02e4364>] (__alloc_skb+0x0/0xf8) from [<c02e4734>] (dev_alloc_skb+0x20/0x44)
Jan 25 11:17:15 LS1 kernel:  r8:c6b8d840 r7:00000024 r6:ffc4c240 r5:ffc4c240 r4:061f8020
Jan 25 11:17:15 LS1 kernel: [<c02e4714>] (dev_alloc_skb+0x0/0x44) from [<c0229f20>] (rxq_refill+0x120/0x194)
Jan 25 11:17:15 LS1 kernel: [<c0229e00>] (rxq_refill+0x0/0x194) from [<c022b514>] (mv643xx_eth_poll+0x344/0x4cc)
Jan 25 11:17:15 LS1 kernel: [<c022b1d0>] (mv643xx_eth_poll+0x0/0x4cc) from [<c02ecb1c>] (net_rx_action+0x190/0x28c)
Jan 25 11:17:15 LS1 kernel: [<c02ec98c>] (net_rx_action+0x0/0x28c) from [<c0048bcc>] (__do_softirq+0x68/0xe0)
Jan 25 11:17:15 LS1 kernel: [<c0048b64>] (__do_softirq+0x0/0xe0) from [<c0049008>] (irq_exit+0x9c/0xa4)
Jan 25 11:17:15 LS1 kernel:  r7:00000000 r6:c0497818 r5:c046cb54 r4:c0464000
Jan 25 11:17:15 LS1 kernel: [<c0048f6c>] (irq_exit+0x0/0xa4) from [<c002b04c>] (__exception_text_start+0x4c/0x60)
Jan 25 11:17:15 LS1 kernel:  r4:00000015
Jan 25 11:17:15 LS1 kernel: [<c002b000>] (__exception_text_start+0x0/0x60) from [<c002b8a8>] (__irq_svc+0x48/0x94)
Jan 25 11:17:15 LS1 kernel: Exception stack(0xc0465f38 to 0xc0465f80)
Jan 25 11:17:15 LS1 kernel: 5f20:                                                       00000000 00000000
Jan 25 11:17:15 LS1 kernel: 5f40: 00000000 60000093 c002d438 c0464000 c0468030 c04849a8 000240dc 41069260
Jan 25 11:17:15 LS1 kernel: 5f60: 00023fa4 c0465f8c c0465f90 c0465f80 c002d34c c002d460 60000013 ffffffff
Jan 25 11:17:15 LS1 kernel:  r7:00000002 r6:00200000 r5:fdd20200 r4:ffffffff
Jan 25 11:17:15 LS1 kernel: [<c002d438>] (default_idle+0x0/0x58) from [<c002d34c>] (cpu_idle+0x5c/0xa4)
Jan 25 11:17:15 LS1 kernel: [<c002d2f0>] (cpu_idle+0x0/0xa4) from [<c037f888>] (rest_init+0x74/0x88)
Jan 25 11:17:15 LS1 kernel:  r7:c0467ec8 r6:c002732c r5:c0484548 r4:c0464000
Jan 25 11:17:15 LS1 kernel: [<c037f814>] (rest_init+0x0/0x88) from [<c0008a54>] (start_kernel+0x250/0x32c)                                         
Jan 25 11:17:15 LS1 kernel:  r4:c048c720
Jan 25 11:17:15 LS1 kernel: [<c0008804>] (start_kernel+0x0/0x32c) from [<00008034>] (0x8034)
Jan 25 11:17:15 LS1 kernel:  r6:c0027730 r5:c0484a0c r4:a0053175
Jan 25 11:17:15 LS1 kernel: Mem-info:
Jan 25 11:17:15 LS1 kernel: DMA per-cpu:
Jan 25 11:17:15 LS1 kernel: CPU    0: hi:   42, btch:   7 usd:   9
Jan 25 11:17:15 LS1 kernel: Active:5779 inactive:20992 dirty:22 writeback:0 unstable:0
Jan 25 11:17:15 LS1 kernel:  free:567 slab:2931 mapped:2725 pagetables:173 bounce:0
Jan 25 11:17:15 LS1 kernel: DMA free:2268kB min:1440kB low:1800kB high:2160kB active:23116kB inactive:83968kB present:130048kB pages_scanned:0 all_unreclaimable? no
Jan 25 11:17:15 LS1 kernel: lowmem_reserve[]: 0 0 0
Jan 25 11:17:15 LS1 kernel: DMA: 389*4kB 71*8kB 1*16kB 2*32kB 1*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 2268kB
Jan 25 11:17:15 LS1 kernel: 24425 total pagecache pages
Jan 25 11:17:15 LS1 kernel: 0 pages in swap cache
Jan 25 11:17:15 LS1 kernel: Swap cache stats: add 28, delete 28, find 0/0
Jan 25 11:17:15 LS1 kernel: Free swap  = 521964kB
Jan 25 11:17:15 LS1 kernel: Total swap = 522072kB
Jan 25 11:17:15 LS1 kernel: 32768 pages of RAM
Jan 25 11:17:15 LS1 kernel: 733 free pages
Jan 25 11:17:15 LS1 kernel: 1519 reserved pages
Jan 25 11:17:15 LS1 kernel: 2931 slab pages
Jan 25 11:17:15 LS1 kernel: 11230 pages shared
Jan 25 11:17:15 LS1 kernel: 0 pages swap cached

They seem to be particularly acute when doing file transfers TO the Linkstation (using either Samba or NFS), and it severely impacts performance (like slowing down to ~ 2 MB/sec. for NFS writes!).

At first I though it was because I was using part of /dev/shm as a ramdisk, but I've since de-configured that and the problem persists. I think it may have something to do with memory fragmentation, but I'm not enough of a kernel guy to know what's going on.

It appears that others using newer armel kernels are seeing similar issues.

Has anybody seen this and come up with any solution/workaround?

Any insights/advice/etc. appreciated...

_________________
Linkstation Live v2 running: pvr on Hauppauge HVR-950, apache, nfs v4, samba, cups, streamripper, Nikon webcam, weather station (via open 2300)


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PostPosted: Wed Jan 28, 2009 7:41 am 
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What MTU are you running with? Are you using jumbo framing for your network?

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LS used as PVR and streaming source


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PostPosted: Wed Jan 28, 2009 10:29 pm 
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lb_worm wrote:
What MTU are you running with? Are you using jumbo framing for your network?

Yes to Jumbo Frames. MTU of 9004. But some of the errors occur with application running strictly on the Linkstation and (AFAIK) not making use of the network. But I'll some testing with a 1500 MTU tonight...

(time passes...)

So resetting the MTU to 1500 DOES seem to alleviate the page allocation failures (with the corresponding drop in performance, of course). I wonder why this is happening with the newer kernels, but not my previous (uImage-2.6.16.57-lsp_eabi-dh_v4) kernel...

Any suggestions for improving the situation? Is it worth trying other MTUs between 1500 and 9000 to try to find a "sweet spot" that doesn't trigger the page allocation failures but brings some of the benefits of Jumbo Frames?

Also, I was just wondering whether anyone has experimented with Martin Michlmayr's DMA patches to try to improve performance with later kernels.

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Linkstation Live v2 running: pvr on Hauppauge HVR-950, apache, nfs v4, samba, cups, streamripper, Nikon webcam, weather station (via open 2300)


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PostPosted: Fri Jan 30, 2009 7:24 am 
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..............


Last edited by dbmoodb on Mon May 25, 2009 4:45 pm, edited 1 time in total.

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PostPosted: Fri Jan 30, 2009 7:57 am 
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I think that this is an ethernet driver problem and it is not handling network buffers correctly. Can you try increasing the min size of /proc/sys/vm/min_free_kbytes to see if this helps?

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PostPosted: Sun Feb 01, 2009 5:45 am 
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lb_worm wrote:
I think that this is an ethernet driver problem and it is not handling network buffers correctly. Can you try increasing the min size of /proc/sys/vm/min_free_kbytes to see if this helps?

Thanks, that seems to have done the trick. I bumped it from the default (1488, I think it was) to 8192 and have done a number of test transfers with Jumbo Frames (mtu 9004) enabled on both sides of the link without a single page allocation failure.

So now my NFS v3 read speeds are back up into the ~ 10-12 MB/sec. range, but write speeds are still tanked (~ 2 MB/sec.). Sigh.

Thanks again for the suggestion!


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PostPosted: Sun Feb 01, 2009 10:50 am 
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With both UDP and TCP?


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PostPosted: Mon Feb 02, 2009 6:27 am 
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I am glad it worked. I have had to do something similar in the past on another machine

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PostPosted: Mon Dec 14, 2009 10:56 am 
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Joined: Mon Apr 09, 2007 9:48 pm
Posts: 130
lb_worm wrote:
I think that this is an ethernet driver problem and it is not handling network buffers correctly. Can you try increasing the min size of /proc/sys/vm/min_free_kbytes to see if this helps?

Well , after change that i start to get :
Dec 14 06:03:25 init: PANIC: segmentation violation! sleeping for 30 seconds.
Dec 14 06:03:55 init: PANIC: segmentation violation! sleeping for 30 seconds.
Dec 14 06:04:25 init: PANIC: segmentation violation! sleeping for 30 seconds.
Dec 14 06:04:55 init: PANIC: segmentation violation! sleeping for 30 seconds.
Dec 14 06:05:25 init: PANIC: segmentation violation! sleeping for 30 seconds.
Dec 14 06:05:55 init: PANIC: segmentation violation! sleeping for 30 seconds.
Dec 14 06:06:25 init: PANIC: segmentation violation! sleeping for 30 seconds.
Dec 14 06:06:55 init: PANIC: segmentation violation! sleeping for 30 seconds.
Dec 14 06:07:25 init: PANIC: segmentation violation! sleeping for 30 seconds.
Dec 14 06:07:55 init: PANIC: segmentation violation! sleeping for 30 seconds.
Dec 14 06:08:25 init: PANIC: segmentation violation! sleeping for 30 seconds.
Dec 14 06:08:55 init: PANIC: segmentation violation! sleeping for 30 seconds.

and on and on ...

I dont know if it is really related but i only start to get this after change /proc/sys/vm/min_free_kbytes to 8192 :)

Anyone knows what that error means ?


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