Re: Regression with calibrate_xor_blocks, probably UML related

[Boaz Harrosh <bharrosh@panasas.com>]

On 02/09/2011 09:02 PM, Boaz Harrosh wrote:
> I have a new module that uses the async_tx.h lib.
> 
> On an exact same module code based on 3.6.37 I see the:
> 	xor: measuring software checksum speed
> 	   8regs     : 11312.000 MB/sec
> 	   8regs_prefetch:  9792.800 MB/sec
> 	   32regs    : 11220.400 MB/sec
> 	   32regs_prefetch:  9750.800 MB/sec
> 	xor: using function: 8regs (11312.000 MB/sec)
> 
> And all is well. But on code based on 2.6.38-rc4 I get hard stuck
> right after:
> 	xor: measuring software checksum speed
> 

OK this is not dependent on Kernel version it is the same for both
.38-rc4 and .37. I was just lucky with .37 more.

And the same things happen with raid456 module. I do
[]$ modprobe raid456; modprobe --remove raid456
A few times it loads, printing the above checks, Then At one
time it freezes. Sometimes at first attempt sometimes at 4-7
attempts. I never went 10 times strait.

When it freezes (hard) I can see in my host that the UML is
at 100% CPU.

BTW: when I manage to pass the tests I get the above numbers
But when I load directly on the host I get:

 xor: automatically using best checksumming function: generic_sse
   generic_sse:  7596.000 MB/sec
 xor: using function: generic_sse (7596.000 MB/sec)
 raid6: int64x1   1660 MB/s
 raid6: int64x2   1832 MB/s
 raid6: int64x4   1566 MB/s
 raid6: int64x8   1175 MB/s
 raid6: sse2x1    3699 MB/s
 raid6: sse2x2    4398 MB/s
 raid6: sse2x4    5863 MB/s
 raid6: using algorithm sse2x4 (5863 MB/s)

and on the UML:

 raid6: int64x1   2019 MB/s
 raid6: int64x2   2208 MB/s
 raid6: int64x4   1892 MB/s
 raid6: int64x8   1528 MB/s
 raid6: using algorithm int64x2 (2208 MB/s)
 xor: measuring software checksum speed
   8regs     : 11308.000 MB/sec
   8regs_prefetch:  9795.600 MB/sec
   32regs    : 11236.000 MB/sec
   32regs_prefetch:  9752.400 MB/sec
 xor: using function: 8regs (11308.000 MB/sec)

So the raid6 sse is better, but comparing it64xX the UML is faster than host
But raid5? that's 33% better results. Does that say that UML's clock has
a bug?

Any way I'm trying to debug that xor.ko loading problem see what
comes up. Any help is welcome

Thanks
Boaz

> the UML is completely frozen. When I kill the uml from the host
> I can sometimes get this trace.
> 





> 750c7498:  [<6005f936>] bad_page+0xd8/0xf3
> 750c74c8:  [<60060c93>] get_page_from_freelist+0x333/0x47b
> 750c7508:  [<60131243>] put_dec+0x20/0x3c
> 750c75a0:  [<6001a0ac>] change_pre_exec+0x0/0x24
> 750c75b8:  [<60060ef1>] __alloc_pages_nodemask+0x116/0x65b
> 750c7668:  [<60132e25>] sprintf+0xa1/0xa3
> 750c76a0:  [<6001a0ac>] change_pre_exec+0x0/0x24
> 750c76b8:  [<60061446>] __get_free_pages+0x10/0x43
> 750c76c8:  [<60012875>] alloc_stack+0x1b/0x1d
> 750c76d8:  [<6001fe27>] run_helper+0x26/0x1b5
> 750c76e8:  [<60021553>] set_signals+0x1c/0x2e
> 750c7708:  [<6007efac>] __kmalloc+0x9e/0xc4
> 750c7748:  [<6001a544>] change+0x124/0x189
> 750c77e8:  [<601b77db>] _raw_spin_unlock+0x9/0xb
> 750c7818:  [<6001a5a9>] close_addr+0x0/0x1c
> 750c7828:  [<6001a5c3>] close_addr+0x1a/0x1c
> 750c7838:  [<6001926a>] iter_addresses+0x5f/0x76
> 750c7858:  [<6007e8e8>] kfree+0x92/0x9b
> 750c7898:  [<60022d01>] tuntap_close+0x24/0x38
> 750c78b8:  [<600194e4>] close_devices+0x4a/0x7f
> 750c78d8:  [<600121bf>] do_uml_exitcalls+0x12/0x23
> 750c78f8:  [<60012cd2>] uml_cleanup+0x1a/0x87
> 750c7928:  [<6002039b>] last_ditch_exit+0x9/0x16
> 750c79e8:  [<78817031>] xor_8regs_2+0x31/0x58 [xor]
> 750c7a18:  [<7881b000>] calibrate_xor_blocks+0x0/0xdf [xor]
> 750c7aa8:  [<601b77ce>] _raw_spin_unlock_irqrestore+0x18/0x1c
> 750c7ac8:  [<60029d8d>] try_to_wake_up+0x86/0x98
> 750c7d78:  [<601b548d>] printk+0xa0/0xa3
> 750c7e08:  [<78817633>] do_xor_speed+0x54/0xaf [xor]
> 750c7e20:  [<7881b000>] calibrate_xor_blocks+0x0/0xdf [xor]
> 750c7e58:  [<7881b057>] calibrate_xor_blocks+0x57/0xdf [xor]
> 750c7e68:  [<7881b000>] calibrate_xor_blocks+0x0/0xdf [xor]
> 750c7e78:  [<6001105a>] do_one_initcall+0x76/0x121
> 750c7eb8:  [<600563fd>] sys_init_module+0x78/0x1a6
> 750c7ee8:  [<60014d60>] handle_syscall+0x58/0x70
> 750c7f08:  [<60024163>] userspace+0x2dd/0x38a
> 750c7fc8:  [<600126af>] fork_handler+0x62/0x69
> 
> (gdb) list *(xor_8regs_2+0x31)
> 0x55 is in xor_8regs_2 (/usr0/export/dev/bharrosh/git/pub/scsi-misc/include/asm-generic/xor.h:29).
> 24                      p1[0] ^= p2[0];
> 25                      p1[1] ^= p2[1];
> 26                      p1[2] ^= p2[2];
> 27                      p1[3] ^= p2[3];
> 28                      p1[4] ^= p2[4];
> 29                      p1[5] ^= p2[5];
> 30                      p1[6] ^= p2[6];
> 31                      p1[7] ^= p2[7];
> 32                      p1 += 8;
> 33                      p2 += 8;
> (gdb) list *(calibrate_xor_blocks+0x0)
> 0xd52 is in calibrate_xor_blocks (/usr0/export/dev/bharrosh/git/pub/scsi-misc/crypto/xor.c:101).
> 96                     speed / 1000, speed % 1000);
> 97      }
> 98
> 99      static int __init
> 100     calibrate_xor_blocks(void)
> 101     {
> 102             void *b1, *b2;
> 103             struct xor_block_template *f, *fastest;
> 104
> 105             /*
> (gdb) list *(do_xor_speed+0x54)
> 0x657 is in do_xor_speed (/usr0/export/dev/bharrosh/git/pub/scsi-misc/crypto/xor.c:84).
> 79                      now = jiffies;
> 80                      count = 0;
> 81                      while (jiffies == now) {
> 82                              mb(); /* prevent loop optimzation */
> 83                              tmpl->do_2(BENCH_SIZE, b1, b2);
> 84                              mb();
> 85                              count++;
> 86                              mb();
> 87                      }
> 88                      if (count > max)
> (gdb) list *(calibrate_xor_blocks+0x57)
> 0xda9 is in calibrate_xor_blocks (/usr0/export/dev/bharrosh/git/pub/scsi-misc/crypto/xor.c:137).
> 132                             "checksumming function: %s\n",
> 133                             fastest->name);
> 134                     xor_speed(fastest);
> 135             } else {
> 136                     printk(KERN_INFO "xor: measuring software checksum speed\n");
> 137                     XOR_TRY_TEMPLATES;
> 138                     fastest = template_list;
> 139                     for (f = fastest; f; f = f->next)
> 140                             if (f->speed > fastest->speed)
> 141                                     fastest = f;
> (gdb) q
> 
> So it looks like the code in UML links the include/asm-generic/xor.h and that it gets
> stuck. Any thing changed in this area in last merge window?
> 
> Before I start the very difficult bisect?
> 
> Thanks for any tips
> Boaz
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