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

[Kok, Auke-jan H]

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.

Auke