Date: Thu, 22 Mar 2007 08:32:23 -0500 From: Eric Anderson <anderson@freebsd.org> To: "roma.a.g" <roma.a.g@gmail.com> Cc: Oliver Fromme <freebsd-performance@freebsd.org> Subject: Re: Slow on heavy I/O operations. Message-ID: <46028567.8080209@freebsd.org> In-Reply-To: <1465093066.20070322162026@gmail.com> References: <1036039198.20070321153412@gmail.com> <200703211354.l2LDsKnV080911@lurza.secnetix.de> <1465093066.20070322162026@gmail.com>
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On 03/22/07 08:20, Roman Gorohov. wrote:
> Hi, Oliver.
> Thanks for explanations.
>
>> Roman Gorohov. <roma.a.g@gmail.com> wrote:
> >> Hello list.
> >> There is a server with FreeBSD FreeBSD 4.11-STABLE(can't upgrade fornow) on HP ProLiant DL140.
> >> Disk system: <SEAGATE ST373207LC 0005> at scbus0 target 0 lun0(pass0,da0) on a ASC-29320A.
> >> If I do:
> >> [idle@hst ~]#dd if=/dev/zero of=bigfile bs=64k count=5000
> >> 5000+0 records in
> >> 5000+0 records out
> >> 327680000 bytes transferred in 37.515699 secs (8734477 bytes/sec)
> >> All is hung while dd working.
> >>
> >> Its look like that:
> >> [idle@hst ~]#systat -v
> >> skip...
> >> Disks da0 pass0 pass1 md0
> >> KB/t 20.33 0.00 0.00 0.00
> >> tps 812 0 0 0
> >> MB/s 16.11 0.00 0.00 0.00
> >> % busy 100 0 0 0
> >> skip...
> >>
> >> [idle@hst ~]#vmstat -w 5
> >> procs memory page disks faults cpu
> >> r b w avm fre flt re pi po fr sr da0 md0 in sy cs us sy id
> >> 1 0 0 1996756 54208 42 23 25 7 39 336 0 0 531 638 404 21 5 74
> >> 1 6 0 2011488 13272 571 0 0 1 2506 8 129 0 1356 2125 159 3 4 93
> >> 4 27 0 2022852 4228 267 0 0 1 1657 4 272 0 1450 784 96 1 3 96
> >> 1 10 0 2027492 40220 449 5 0 12 3257 9384 574 0 1773 4366 189 8 7 85
> >> 1 10 0 2035064 25604 746 2 1 7 2965 4466 157 0 1380 4486 184 8 7 85
> >> 0 11 0 2030860 4228 515 2 1 3 2098 31 214 0 1412 3077 149 16 5 79
> >> 3 14 0 2042792 10004 1014 4 1 5 2787 4432 267 0 1440 1735 118 2 4 94
> >> 2 16 0 2062664 4228 301 0 1 2 2843 27 564 0 1759 1250 107 5 4 91
> >>
> >> [idle@hst ~]#iostat -w 5
> >> tty da0 pass0 pass1 cpu
> >> tin tout KB/t tps MB/s KB/t tps MB/s KB/t tps MB/s us ni sy in id
> >> 0 25 0.00 0 0.00 0.00 0 0.00 0.00 0 0.00 21 0 4 0 74
> >> 1 109 62.56 242 14.81 0.00 0 0.00 0.00 0 0.00 7 0 9 0 83
> >> 0 101 18.29 433 7.73 0.00 0 0.00 0.00 0 0.00 2 0 2 0 95
> >> 0 76 26.45 281 7.25 0.00 0 0.00 0.00 0 0.00 3 0 4 0 93
> >> 0 94 15.99 357 5.57 0.00 0 0.00 0.00 0 0.00 2 0 2 0 96
> >> 0 15 16.04 667 10.45 0.00 0 0.00 0.00 0 0.00 0 0 3 1 96
> >> 0 93 15.99 558 8.71 0.00 0 0.00 0.00 0 0.00 0 0 2 1 97
> >> 0 80 16.16 252 3.98 0.00 0 0.00 0.00 0 0.00 0 0 1 0 98
> >> 0 117 23.44 240 5.49 0.00 0 0.00 0.00 0 0.00 9 0 6 0 85
> >>
> >> Why this happen?
>
>> The numbers from your vmstat output indicate that your
>> machine is paging ("swapping"), i.e. it's running out
>> or RAM.
>
> That seems like true, and I forget to mention that 2/3 of swap is
> located at physical disk(da0).
> [idle@hst ~]#swapinfo
> Device 1K-blocks Used Avail Capacity Type
> /dev/da0s1b 524160 463300 60860 88% Interleaved
> /dev/rvn0b 1048448 578724 469724 55% Interleaved
> Total 1572608 1042024 530584 66%
>
> But what I can't understand - why such non-critical(as it seems to me) disk activity,
> cause 100% busyness for disk? Its claim to be 40.000MB/s transfers, but
> sometimes its 100% busy when iostat show only 1 MB/s.
If the disks are truly busy, then the heads might be wiggling away all
your 40MB/s due to seeks. Run gstat and see what it shows also.
I don't think you can do any real tests while the machine is swapping,
since that will most likely destroy any notion of performance for you.
The dd test you did above also isn't that accurate, because you were
writing to a file system on the disk, and that can change your
performance quite a bit depending on a lot of factors based on the file
system.
Eric
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