[systemd-devel] bootchart issues on slow hardware

[Kay Sievers]

On Mon, Mar 18, 2013 at 7:40 PM, Kok, Auke-jan H
<auke-jan.h.kok at intel.com> wrote:
> On Sun, Mar 17, 2013 at 6:54 AM, Kay Sievers <kay at vrfy.org> wrote:
>> Here is a chart:
>>   http://people.freedesktop.org/~kay/bootchart-20130317-1434.svg
>>
>> Rotating media and really cheap hardware looks very sad, and we take
>> like 5 times longer to boot than Windows 8.
>
> I've seen many charts like that - in most of them it appears like
> readahead isn't helping at all.

Yeah, it actually hurts, it's faster without it.

I put an SSD in that crappy box today; it's down from 25 to 7 sec on
the otherwise identical system. :)

So I'll not need to debug any rotating media issues, I don't have any
of them again. :)

>> Why does bootchart stop before all the *really* slow desktop stuff starts?
>
> There's some rework needed to make it stop in the same way that e.g.
> the readahead collector works - right now it just runs for 20 seconds
> or so and exits. This is on my work list to fix.

Ah, yeah, systemd can probably supply that info.

>> Why does bootchart claim an idle time of ~5 sec, not that I wouldn't
>> like that, but .... :)
>
> That's when the CPU are below a certain percentage(somewhere below 1%)
> for a certain time (0.5sec)... enough to call "idle". Usually this
> happens when there is really slow IO. It bears no correlation to the
> systemd state.

I see.

The heavy concurrency of systemd with a filesystem that does not
optimize itself for that, just isn't working too well on rotating
media. :)

Kay