<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Apr 26, 2018 at 4:29 PM, Ludovic Brenta <span dir="ltr"><<a href="mailto:ludovic@ludovic-brenta.org" target="_blank">ludovic@ludovic-brenta.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><span class="gmail-">On Thu, 26 Apr 2018 16:06:17 +0200, Michael Stapelberg wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
- ext2 instead of ext4 for the root partition (SD cards are slow<br>
and do not need a journalling file system which would only slow<br>
them down even more, I think).<br>
</blockquote>
<br>
Do you have any benchmarks/measurements supporting this claim? This<br>
is the first time I hear about it.<br>
</blockquote>
<br></span>
I have no benchmarks but I know that a journal must be written to<br>
*in addition to* the regular file data and meta-data. This not only<br>
uses additional bandwidth (which is not normally noticeable on a<br>
6 Gbit/s link like SATA-3 but may be on USB 2.0 or SD card) but also<br>
creates a hot-spot on the device containing the journal (and this is<br>
probably bad for low-end devices like an SD card).</blockquote><div><br></div><div><a href="https://thunk.org/tytso/blog/2009/03/01/ssds-journaling-and-noatimerelatime/">https://thunk.org/tytso/blog/2009/03/01/ssds-journaling-and-noatimerelatime/</a> is somewhat dated, but looks credible (tytso is the lead developer of the ext* series of file systems). I wouldn’t be too worried about the extra bandwidth, especially as the trade-off is between fast, but easily corrupt and slower, but robust.<br></div><div><br></div><div><a href="https://www.raspberrypi.org/forums/viewtopic.php?t=142626">https://www.raspberrypi.org/forums/viewtopic.php?t=142626</a> talks about wear leveling (which addresses your hotspot concern).<br></div><div><br></div><div>In summary, I think using ext4 on any but the cheapest no-name SD cards should be fine for the majority of our users.</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><span class="gmail-"><br>
<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
The other change is that python3.6-minimal has been upgraded from<br>
3.6.4-3 in your latest image to 3.6.5~rc1-1 (testing) and 3.6.5-3<br>
(unstable). And this package is giving me the following<br>
headache:<br>
<br>
qemu: uncaught target signal 11 (Segmentation fault) - core dumped<br>
<br>
while executing the post-installation script of python3.6-minimal.<br>
As a consequence, all subsequent invocations of apt install will<br>
also fail as they notice the package is unconfigured and<br>
re-execute<br>
the postinst script.<br>
<br>
I think this may be due to the lack of support for threading in<br>
qemu, combined with the use of pipes in the postinst script.<br>
</blockquote>
<br>
I would be surprised if qemu did not support threading. Have you<br>
searched for bug reports about this symptom?<br>
</blockquote>
<br></span>
Yes and I found these:<br>
<a href="http://qemu.11.n7.nabble.com/Uncaught-target-signal-11-Segmentation-fault-core-dumped-tp290467p290775.html" rel="noreferrer" target="_blank">http://qemu.11.n7.nabble.com/U<wbr>ncaught-target-signal-11-Segme<wbr>ntation-fault-core-dumped-<wbr>tp290467p290775.html</a><br>
<a href="https://stackoverflow.com/questions/15086238/error-qemu-uncaught-target-signal-11-segmentation-fault" rel="noreferrer" target="_blank">https://stackoverflow.com/ques<wbr>tions/15086238/error-qemu-unca<wbr>ught-target-signal-11-segmenta<wbr>tion-fault</a><br>
<br>
but I realize thay they may be outdated now. I was also led to<br>
understand that qemu did not support threading for ~10 years,<br>
maybe this has finally been implemented since.<br>
<br>
Also, no bug reports specifically for my problem. And I am not<br>
yet certain this is a bug so I wanted to ask you before I filed one.<span class="gmail-HOEnZb"><font color="#888888"><br>
<br>
-- <br>
Ludovic Brenta.<br>
<br>
</font></span></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature">Best regards,<br>Michael</div>
</div></div>