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From: "Kailash Kailash" <kailash.kailash@zscaler.com>
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Date: Wed, 18 Feb 2009 12:44:53 -0800
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Subject: FreeBSD 7.O compiled code is very slow
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I am using FreeBSD 7.0 in 64 BIT mode. Same code compiled on BSD 7.0 runs
50% speed (as expected by CPU and code architecture) compared to BSD 6.2.
Here is one real code with binary output. On 3.0 GHz Woodcrest processor, I
am able to copy from one cache to another cache at the speed of
24Gbytes/second verses 12 Gbytes/second. Any help is appreciated.

Thanks,

Kailash

 

Source-code:

#define BACKWARD_MEMCOPY_WITH_TYPE(dp, sp, len, type)
BACKWARD_MEMCOPY((type*)(dp), (const type*)(sp),
((len)+(sizeof(type)-1))/sizeof(type))

 

#define BACKWARD_MEMCOPY(dp, sp, len) \

do { \

        smwbits __len = len;            /* must be signed value */ \

        while (--__len >= 0) \

                (dp)[__len] = (sp)[__len]; \

} while (0)

 

BSD 6.2 code 

0x00000000004353b2 <smcli_memory_copy_performance+434>: mov
0x8(%rbp,%rdx,8),%rax

0x00000000004353b7 <smcli_memory_copy_performance+439>: mov
%rax,0x48(%r12,%rdx,8)

0x00000000004353bc <smcli_memory_copy_performance+444>: dec    %rdx

0x00000000004353bf <smcli_memory_copy_performance+447>: jns    0x4353b2
<smcli_memory_copy_performance+434>

 

BSD 7.0 code

0x000000000040cb80 <smcli_memory_copy_performance+272>:        mov
0xfffffffffffffff8(%rsi),%rax

0x000000000040cb84 <smcli_memory_copy_performance+276>:        mov
%rax,0xfffffffffffffff8(%rcx)

0x000000000040cb88 <smcli_memory_copy_performance+280>:        sub
$0x8,%rsi

0x000000000040cb8c <smcli_memory_copy_performance+284>:        sub
$0x8,%rcx

0x000000000040cb90 <smcli_memory_copy_performance+288>:        sub
$0x1,%rdx

0x000000000040cb94 <smcli_memory_copy_performance+292>:        jns
0x40cb80 <smcli_memory_copy_performance2+272>