Re: [RFT] Port 0x80 I/O speed

["Török Edwin" <edwintorok@gmail.com>]

Rene Herman wrote:
> Good day.
>
> Would some people on x86 (both 32 and 64) be kind enough to compile
> and run the attached program? This is about testing how long I/O port
> access to port 0x80 takes. It measures in CPU cycles so CPU speed is
> crucial in reporting.
>
> Posted a previous incarnation of this before, buried in the outb 0x80
> thread which had a serialising problem. This one should as far as I
> can see measure the right thing though. Please yell if you disagree...
>
Hi,

Tested on 2 systems.

System I
------------
processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 47
model name      : AMD Athlon(tm) 64 Processor 3200+
stepping        : 2
cpu MHz         : 2000.000
cache size      : 512 KB
fpu             : yes
fpu_exception   : yes

Motherboard: Asus A9N-E


With -m32:

edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067
edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067
edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067
edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067
edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067
edwin@lightspeed2:~$ sudo ./port80
cycles: out 619, in 583
edwin@lightspeed2:~$ sudo ./port80
cycles: out 619, in 583
edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067
edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067
edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067
edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067
edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067

After making the __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
I get this with 64:
edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067
edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067
edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067
edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067
edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067
edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067
edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067
edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067
edwin@lightspeed2:~$ sudo ./port80
cycles: out 618, in 583
edwin@lightspeed2:~$ sudo ./port80
cycles: out 618, in 583
edwin@lightspeed2:~$ sudo ./port80
cycles: out 1107, in 1067

If I stop cpudyn I get a constant 618/583.

System II
------------

processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 14
model name      : Genuine Intel(R) CPU           T2300  @ 1.66GHz
stepping        : 8
cpu MHz         : 1667.000
cache size      : 2048 KB
physical id     : 0
siblings        : 2

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 6
model           : 14
model name      : Genuine Intel(R) CPU           T2300  @ 1.66GHz
stepping        : 8
cpu MHz         : 1667.000
cache size      : 2048 KB
physical id     : 0
siblings        : 2


Dell Inspiron 6400, Intel Core Duo (ICH7 chipset)

thunder:/home/edwin# ./port80
cycles: out 2480, in 1867
thunder:/home/edwin# ./port80
cycles: out 2482, in 1865
thunder:/home/edwin# ./port80
cycles: out 2968, in 1893
thunder:/home/edwin# ./port80
cycles: out 1991, in 1372
thunder:/home/edwin# ./port80
cycles: out 1979, in 1366
thunder:/home/edwin# ./port80
cycles: out 2473, in 1865
thunder:/home/edwin# ./port80
cycles: out 2484, in 1869

After setting CPU governor to performance:

# ./port80
cycles: out 2368, in 1783
thunder:/home/edwin# ./port80
cycles: out 2377, in 1783
thunder:/home/edwin# ./port80
cycles: out 2367, in 1774
thunder:/home/edwin# ./port80
cycles: out 2370, in 1780
thunder:/home/edwin# ./port80
cycles: out 2365, in 1782
thunder:/home/edwin# ./port80
cycles: out 2369, in 1774
thunder:/home/edwin# ./port80
cycles: out 2366, in 1784
thunder:/home/edwin# ./port80
cycles: out 2379, in 1786
thunder:/home/edwin# ./port80
cycles: out 2367, in 1773
thunder:/home/edwin# ./port80
cycles: out 2376, in 1783
thunder:/home/edwin# ./port80
cycles: out 2360, in 1784
thunder:/home/edwin# ./port80
cycles: out 2367, in 1783
thunder:/home/edwin# ./port80
cycles: out 2370, in 1783
thunder:/home/edwin# ./port80
cycles: out 2382, in 1782

Also tried in a loop, but values are not constant:
while true; do ./port80; done
cycles: out 2415, in 1818
cycles: out 2405, in 1817
cycles: out 2414, in 1810
cycles: out 2411, in 1819
cycles: out 2407, in 1821
cycles: out 2410, in 1820
cycles: out 2418, in 1821
cycles: out 2408, in 1847
cycles: out 2404, in 1805
cycles: out 2411, in 1858
cycles: out 2395, in 1765
cycles: out 2377, in 1786
cycles: out 2378, in 1813
cycles: out 2395, in 1800
cycles: out 2381, in 1793
cycles: out 2382, in 1790
cycles: out 2399, in 1835
cycles: out 1928, in 1327
cycles: out 2410, in 1781
cycles: out 1996, in 1287
cycles: out 2369, in 1768
cycles: out 2401, in 1805
cycles: out 2395, in 1802
cycles: out 2389, in 1786
cycles: out 2359, in 1768
cycles: out 2495, in 1858
cycles: out 2408, in 1809
cycles: out 2919, in 1859
cycles: out 2404, in 1798
cycles: out 2393, in 1791
cycles: out 2882, in 1797
cycles: out 2404, in 1789
cycles: out 2406, in 1785
cycles: out 2393, in 1840
cycles: out 2498, in 1818
cycles: out 2402, in 1805
cycles: out 2888, in 1858
cycles: out 2397, in 1802
cycles: out 2411, in 1810
cycles: out 2396, in 1788
cycles: out 2362, in 1780
cycles: out 2861, in 1785
cycles: out 2380, in 1780
cycles: out 2357, in 1785
cycles: out 2342, in 1783
cycles: out 1916, in 1294
cycles: out 2358, in 1768
cycles: out 2371, in 1763
cycles: out 2386, in 1783
cycles: out 1919, in 1320
cycles: out 2355, in 1782
cycles: out 2330, in 1787
cycles: out 2350, in 1781
cycles: out 1881, in 1269
cycles: out 2378, in 1768
cycles: out 2381, in 1739
cycles: out 2365, in 1768
cycles: out 2362, in 1759
cycles: out 2368, in 1739
cycles: out 2354, in 1775
cycles: out 2375, in 1783
cycles: out 2369, in 1785
cycles: out 2361, in 1769
cycles: out 2382, in 1785
cycles: out 2370, in 1783


--Edwin