Re: SATA-performance: Linux vs. FreeBSD

Martin A. Fink
2007-02-12T16:37:22Z

Some more info:

:~> strace -c -T -o trace.out dd if=/dev/zero of=test.txt bs=10MB count=200

200+0 Datensätze ein
200+0 Datensätze aus
2000000000 bytes (2,0 GB) copied, 52,8632 seconds, 37,8 MB/s

test.txt:

% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
93.26 6.845265 33555 204 write
6.41 0.470283 11757 40 18 open
0.32 0.023687 116 205 read
0.00 0.000149 9 16 mmap2
0.00 0.000119 40 3 munmap
0.00 0.000081 3 24 close
0.00 0.000068 6 11 old_mmap
0.00 0.000064 3 20 fstat64
0.00 0.000040 4 10 rt_sigaction
0.00 0.000036 12 3 madvise
0.00 0.000014 7 2 clock_gettime
0.00 0.000010 3 3 brk
0.00 0.000008 8 1 _sysctl
0.00 0.000007 7 1 1 access
0.00 0.000006 6 1 mprotect
0.00 0.000005 5 1 futex
0.00 0.000004 4 1 uname
0.00 0.000004 4 1 _llseek
0.00 0.000003 3 1 rt_sigprocmask
0.00 0.000003 3 1 getrlimit
0.00 0.000003 3 1 set_thread_area
0.00 0.000003 3 1 set_tid_address
------ ----------- ----------- --------- --------- ----------------
100.00 7.339862 551 19 total

This means, that the CPU is only 7.3 of 52.8 seconds working. This is what one
can hear: If I run programs where the time they need is the same time as
strace says, then I have 100% CPU load and the cpu fan starts to blow
heavily. In the case here, the heat fan does not do anything. It looks like
the SATA driver simply blocks the CPU while doing whatever...