[yocto] Some data collection and analysis on poky performance

[Tian, Kevin]

>From: Qing He
>Sent: Wednesday, October 27, 2010 5:23 PM
>
>As we know, many of us have experienced slow builds of recent poky,
>and it also takes larger disk space. This affects user exprience thus
>is one of our directions in 1.0.

thanks Qing, that's a great start.

>
>To find the problems leading to performance issues, I tried some
>profiling on poky builds, below is a very brief summary of the data.
>I profiled poky-image-minimal of both the current master branch and
>green release, with similar parameters (4 CPUs) on NHM. Note that
>both rpm and ipk packages are built for current master branch, while
>oonly ipk packages are built for green release
>
>
>I. some stats
>1. recipes (including -native)
>  green release:
>    recipes built:  76
>    tasks run:  998
>  master:
>    recipes built: 133
>    tasks run:  1600

could you get a compare list which recipes have been newly added? I thought that
minimal image was seldom changed...

>
>2. time
>  green release:
>    real:  28m7s
>    user:  57m45s
>    sys:    9m41s
>    user+sys: 67m26s
>  master:
>    real:  66m39s
>    user: 152m17s
>    sys:   27m37s
>    user+sys: 179m54s
>
>3. space (haven't analyze though)
>  green release:   7.8G
>  master:         26.6G

I recall that RP mentioned debug symbol is enabled in current master, but I'm not sure
whether green has done the same. You may double-confirm that part first.

>
>
>II. profiling
>I tried a brief profile by collecting the time used for every task, so
>we can scrutinize the result from a microscopic point of view. I'm still
>looking into the full result, but there's something of immediate
>attention.
>
>In master, hardly any task consume less than 1.3s, this is quite
>surprising, since many tasks like do_patch virtually do nothing, while
>in the green release, these tasks may simply consume 0.1~0.2s. A deeper
>investigation shows that this large overhead goes to bitbake-runtask,
>the bitbake config and cache mechanism is executed for every task,
>considerably increased the time. The overhead introduced solely by
>this is around 1600*1.3=2080s, approximately 35 minutes (user+sys).

It's said this change comes from pseudo integration. Now it's time for us to
revisit this implementation then. RP can have more insights here.

>
>Also, we should count the additional rpm packaging system,
>do_package_write_rpm costs around 1400s, (excluding 1.3s per task,
>btw, this is about 50% slower than do_package_write_ipk, in average),
>that's around 23 minutes.
>
>Roughly considering that the build time is proportional to recipes
>count, we can try to estimate master build time from green release:
>    67 * (76 / 133) + 35 + 23 = 175
>very close to the real time consuming (although somewhat too closed...),
>so possibly the above two are the most significant time consumers
>in the slowness of current poky
>

above are all good findings!

Thanks
Kevin