32/64 bits: what to choose for old laptop?

eccerr0r · Posted: Fri Oct 05, 2018 10:09 pm Post subject:

Yeah, I took a chunk out of my SSD's life trying to compile I believe it was webkit or qt. I only had 3 processes going on this dual core (-j3) with 2GB RAM, and it was swapping quite a bit though it was kind of hard to notice since it swaps fairly quickly.

The SSD is now probably getting close to a decade old, and I just hit... 1% lifetime usage (it's now about 30 erase cycles on the MLC). Portage_tmpdir is on the SSD as well. That last huge batch update I did on this SSD took around ~2 erase cycles to complete, and the swapping was a good chunk of it... and having to restart broken merges kills...
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josephg · Posted: Fri Oct 05, 2018 10:56 pm Post subject:

that's why i have -gk in make.conf on my netbook

Jaglover · Posted: Sat Oct 06, 2018 12:08 am Post subject:

My solution to this problem is building in NFS chroot. Puts minimal load to the hardware, except the NIC. No 32 bit here.
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josephg · Posted: Sat Oct 06, 2018 12:11 am Post subject:

that's interesting.. i wonder if you can cross compile arm in nfs chroot from intel

eccerr0r · Posted: Sat Oct 06, 2018 12:14 am Post subject:

Actually build memory use isn't the problem, the fact that build memory use is high, all other operations on that computer like running Firefox, etc., is also high, and performance will suffer likewise.

However if you still do not completely use up all your RAM, then maybe things are okay. I just felt that amd64 2GB machine even when not compiling seemed to use up all RAM well before my x86 machine did with 2GB RAM.
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josephg · Posted: Sat Oct 06, 2018 12:26 pm Post subject:

one of the reasons i still continue with 32bit on all my systems

1clue · Advocate Joined: 05 Feb 2006 Posts: 2569

IMO Gentoo is not happy in 2 GiB no matter what. I think that anything under 4 and you want to have a compiler farm with bigger hardware somewhere on your network.

I have successfully installed Gentoo on a Raspberry Pi B+ without the compiler farm, but when I was done I pretty much trashed it as it would be a full-time job just to do updates on it.

eccerr0r · Posted: Sat Oct 13, 2018 4:42 pm Post subject:

I tried chrooting into my nfs mounted Atom from my i7...

When I tried running 'emerge' I got greeted with:

tribute58 · n00b Joined: 14 Oct 2018 Posts: 7

I'm running Gentoo with 64bit kernel + userspace on an Acer Aspire One D255 (Atom N550 1.5GHz dualcore + HT with max 2GB Ram). And it works!

The only problematic package, in case of ram, is chromium. It didn't respect -jn and ran with at least 8 threads, if I remember correctly. Maybe one can override it... I didn't dig into this as I use firefox, which compiles just fine.

My make.conf uses march=native -O2 pipe and -j2! Running updates over night is not a problem as long as you don't try to experiment with LTO.

The only bin package I'm using is LibreOffice, but thats a question of CPU performance...

I don't think -Os helps, neither compiling nor running programs, but I never checked that. Of course, it reduces the instruction memory footprint, but has no influence on data, so the overall gain will be negligible.

eccerr0r · Posted: Sun Oct 14, 2018 3:18 pm Post subject:

My Atom 32 bit with 2GB RAM is still chugging away at updates. It was compiling rust when I looked at it last night, and is STILL compiling rust this morning...

cord · Guru Joined: 28 Apr 2007 Posts: 346

How long dev-qt/qtwebkit compilation took?

eccerr0r · Posted: Sun Oct 14, 2018 7:45 pm Post subject:

I don't have qtwebkit or webkit-gtk installed on this machine, plus sometimes I have distcc working and sometimes not, so hard to tell which merges were done under what circumstances.

Also not sure why I have a few entries with really short merge times, but this one is probably accurate:

rust: Sat Oct 13 20:27:49 2018: 57930 seconds

Gcc is bad too, this is 7.3:
gcc: Sat Oct 13 09:19:24 2018: 27702 seconds

32-bit -- so far, neither package swaps while building using MAKEOPTS=-j2 (since this Atom is a dual thread machine.) on 2GB.

The 64-bit setup seems more swappy with the same amount of RAM. Alas overall speed is faster for the 64-bit because that's a Core2 Duo which is many times faster than the dual thread single core Atom.
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n05ph3r42 · Tux's lil' helper Joined: 11 Jul 2016 Posts: 135

cord:
As for hardware RAM limitations - i suggest to try other RAM, better of same manufacturer, same as soldered on your mb. Mostly this "limitations" is only in specifications.

Also you can try https://wiki.gentoo.org/wiki/Distcc to speedup compilation, if you have other machines on your network.

tribute58 · n00b Joined: 14 Oct 2018 Posts: 7

eccerr0r · Posted: Thu Nov 08, 2018 6:13 am Post subject:

BTW, portage/"emerge" uses ~500MB of RAM on an amd64 box I'm updating right now (2GB RAM) ... a quarter of its RAM is used by portage for emerge!

I suspect I'm not comparing apples with apples, but a 32-bit install I'm maintaining, emerge used up about 252MB of RAM. The difference: the 32-bit install (1GB RAM...) has an xfce4 setup, other 64-bit has full GNOME setup too; both have firefox-60 and its dependencies.

Anyone see similar memory use? No wonder the 2GB amd64 machine is running fairly crappy when doing updates.
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cord · Guru Joined: 28 Apr 2007 Posts: 346

eccerr0r · Posted: Thu Nov 15, 2018 8:05 pm Post subject:

Those don't make portage use much memory. Anyway --sync could be using rsync or git I believe, webrsync is rsync. Both use an external program to do the sync and isn't really using portage.

Doing the dependency calculations unfortunately is serialized with doing the actual make compilation, unlike doing a sync which does not need to be (and should not be) running while computing dependencies...
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Anon-E-moose · Posted: Thu Nov 15, 2018 8:08 pm Post subject:

cord · Guru Joined: 28 Apr 2007 Posts: 346

It needs 500 MiB RAM to unpack 50 MiB archive?

eccerr0r · Posted: Fri Nov 16, 2018 5:25 pm Post subject:

No... again, 500MB to compute dependencies. When doing a sync, dependencies are not computed - heck, portage doesn't even load the ebuilds to compute anything...
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eccerr0r · Posted: Thu Nov 29, 2018 6:28 pm Post subject:

For curiosity sake, dev-lang/rust of the few runs I tried took:

Atom 1.6GHz dual thread, 32-bit: 16 hours (std dev less than 5 mins)
Pentium-M 1.6GHz single thread, 32-bit: 7 hours (std dev is on the order of an hour, so I have to get more accurate data...)

I have to use rust as a gauge because rust does not distribute, so I know it's not cheating :)

Anyway, I didn't expect this kind of discrepancy, thought the two processors were closer together in terms of speed. Alas the Atom is not affected by meltdown or other CPU security issues...

I will need to do some testing of 32- vs 64- bit. The only data I have right now is flawed:
32 bit QEMU KVM using 2 cores on Core2Quad 9550S: just under 3 hours
64bit baremetal using 4 cores on Core2Quad 9550S: just over 1 hour.

If I extrapolate the 32-bit number, it would be under 1.5 hours in 32 bit. That would mean that QEMU is quite slow adding 50% time penalty or 33% speed penalty... Of course this has no bearing on 32- vs 64- on baremetal.
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Marcih · Apprentice Joined: 19 Feb 2018 Posts: 213

1clue · Advocate Joined: 05 Feb 2006 Posts: 2569

eccerr0r · Posted: Thu Nov 29, 2018 9:57 pm Post subject:

The atom is an old n270 single core dual thread, the Pentium-M is just a Dothan 1.6GHz.

I also suspect that the "rust" workload is really not what an atom is designed for. I haven't had a definitive distcc-less gcc run to compare but I suspect gcc also isn't quite a "normal" workload.

On the other hand firefox itself seems about the same or maybe a tad worse on the Pentium-M and the Atom. But I haven't run a true benchmark on them to compare, but I would think that a browser should be in the intended workloads of the Atom...
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