[systemd-devel] systemd-udevd: excessive I/O usage

[Peeters Simon]

2012/6/4 Peeters Simon <peeters.simon at gmail.com>:
> 2012/6/4 Kok, Auke-jan H <auke-jan.h.kok at intel.com>:
>> On Mon, Jun 4, 2012 at 1:14 PM, Peeters Simon <peeters.simon at gmail.com> wrote:
>>> 2012/6/4 Kok, Auke-jan H <auke-jan.h.kok at intel.com>:
>>>> On Mon, Jun 4, 2012 at 12:49 PM, Peeters Simon <peeters.simon at gmail.com> wrote:
>>>>> Hello all.
>>>>>
>>>>> while trying to optimize my bootup i noted that i could not squeeze it
>>>>> under 17seconds userspace
>>>>>
>>>>> Looking at the bootchart revealed that this is mainly due to
>>>>> systemd-udevd consuming 60% of my bootup I/O.
>>>>> This means i lose 12 seconds of bootup just to one process.
>>>>
>>>> can you post the bootchart SVG file?
>>>>
>>>> I'm assuming you're using this version of bootchart:
>>>>
>>>> http://foo-projects.org/~sofar/bootchart/bootchart-1.18.tar.gz
>>> apparently not, i did just yum install bootchart and it reports to be
>>> version 0.14, will take a look at this version.
>>>>
>>>>> i was wondering whether there is any way to get this more optimized?
>>>>> fewer udev rules? more readahead? something else? (i have no idea what
>>>>> this I/O is, except for the fact that it is scattered all over the
>>>>> place)
>>>>>
>>>>> this was with systemd 184(from fedora18) on fedora 17.
>>>>
>>>> The bootchart SVG will tell us most of the stuff that want to know -
>>>> so please share it.
>>> here you are (this is with fedoras default bootchart, will try the
>>> other one later.)
>>
>> the old version obscures a lot of information - in this case all the IO
>> gets attributed to udev while in fact it's probably one of your kernel
>> threads. The version of bootchart I maintain should provide a much
>> clearer picture of where the bottlenecks are.
>
> well, here it is, it does not really show the I/O activity the old one
> shows (it seems like this one only shows throughput)

actually, here it is (forgotten attachment)

> between 9 and 15 seconds almost nothing seems to happen, almost no
> cpu, almost no I/O throughput, only the sound of my harddisk seeking
> the whole time, could it be because udev spawns so many children that
> want access to the disk simultaneously?
>
> simon
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