Re: Possible dcache BUG

[Udo A. Steinberg]

On Thu, 12 Aug 2004 18:31:31 -0700 (PDT) Linus Torvalds (LT) wrote:

LT> Your slab usage seems to be:
LT> 
LT> 	cumulative	     usage	name
LT> 	=========	    ======	====
LT> 		.....
LT> 	  2,021,428	   151,552	pgd
LT> 	  2,182,804	   161,376	size-96
LT> 	  2,367,124	   184,320	biovec-(256)
LT> 	  2,559,124	   192,000	biovec-128
LT> 	  2,751,124	   192,000	biovec-64
LT> 	  2,997,076	   245,952	ext3_inode_cache
LT> 	  3,255,124	   258,048	size-1024
LT> 	  3,545,940	   290,816	size-512
LT> 	  3,843,468	   297,528	radix_tree_node
LT> 	  4,153,932	   310,464	inode_cache
LT> 	  4,494,972	   341,040	dentry_cache
LT> 	  4,994,684	   499,712	size-8192
LT> 	  5,912,188	   917,504	size-32768
LT> 	105,397,820	99,485,632	size-64
LT> 
LT> Something pretty much stands out.
LT> 
LT> What the _heck_ is doing 64-byte allocations and leaking them?
LT> 
LT> Can you figure out what triggers it for you? If nothing obvious comes to 
LT> mind, could you do something really silly like this

[...]

Linus,

So far I have had serious trouble reproducing the slab misbehaviour quoted
above. However, I've just come across what appears to be a serious VM or USB
problem which may or may not be related to that, and I can reproduce it.

I've tried to download 700 MB of data from a digital camera via USB using
"gphoto2 --get-all-files" and I can repeatedly run my 128 MB box out of
memory using either Linux 2.4.26 or 2.6.8.1 for that.


2.4.26 fails with

Aug 19 23:02:05 laptop kernel: __alloc_pages: 0-order allocation failed (gfp=0x1d2/0)
Aug 19 23:02:05 laptop kernel: __alloc_pages: 0-order allocation failed (gfp=0x1f0/0)
Aug 19 23:02:05 laptop kernel: __alloc_pages: 0-order allocation failed (gfp=0x1d2/0)

2.6.8.1 fails with

Aug 19 21:27:41 laptop kernel: usb 1-1: usbfs: interface 0 claimed while 'gphoto2' sets config #1
Aug 19 21:46:43 laptop kernel: oom-killer: gfp_mask=0x1d2                                        
Aug 19 21:46:43 laptop kernel: DMA per-cpu:
Aug 19 21:46:43 laptop kernel: cpu 0 hot: low 2, high 6, batch 1 
Aug 19 21:46:43 laptop kernel: cpu 0 cold: low 0, high 2, batch 1
Aug 19 21:46:43 laptop kernel: Normal per-cpu:
Aug 19 21:46:43 laptop kernel: cpu 0 hot: low 14, high 42, batch 7
Aug 19 21:46:43 laptop kernel: cpu 0 cold: low 0, high 14, batch 7
Aug 19 21:46:43 laptop kernel: HighMem per-cpu: empty             
Aug 19 21:46:43 laptop kernel: 
Aug 19 21:46:43 laptop kernel: Free pages:        1324kB (0kB HighMem)
Aug 19 21:46:43 laptop kernel: Active:1315 inactive:27343 dirty:0 writeback:0 unstable:0 free:331 slab:1606 mapped:1555 pagetables:241
Aug 19 21:46:43 laptop kernel: DMA free:704kB min:44kB low:88kB high:132kB active:0kB inactive:10720kB present:16384kB                
Aug 19 21:46:43 laptop kernel: protections[]: 22 178 178
Aug 19 21:46:43 laptop kernel: Normal free:620kB min:312kB low:624kB high:936kB active:5260kB inactive:98652kB present:114688kB
Aug 19 21:46:43 laptop kernel: protections[]: 0 156 156
Aug 19 21:46:43 laptop kernel: HighMem free:0kB min:128kB low:256kB high:384kB active:0kB inactive:0kB present:0kB
Aug 19 21:46:43 laptop kernel: protections[]: 0 0 0
Aug 19 21:46:43 laptop kernel: DMA: 0*4kB 2*8kB 5*16kB 5*32kB 1*64kB 1*128kB 1*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 704kB   
Aug 19 21:46:43 laptop kernel: Normal: 1*4kB 3*8kB 3*16kB 1*32kB 0*64kB 0*128kB 0*256kB 1*512kB 0*1024kB 0*2048kB 0*4096kB = 620kB
Aug 19 21:46:43 laptop kernel: HighMem: empty
Aug 19 21:46:43 laptop kernel: Swap cache: add 366080, delete 339455, find 219744/259874, race 0+0
Aug 19 21:46:43 laptop kernel: Out of Memory: Killed process 10239 (gphoto2).        

-Udo.

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