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Michael Zucchi

 B.E. (Comp. Sys. Eng.)

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Friday, 01 December 2017, 08:22

RAM saga

Powered down last night because of an approaching thunderstorm ... half my ram gone again.

disable_mtrr_cleanup did nothing. disable_mtrr_trim would hang the boot.

I noticed the RAM speed was wrong in the BIOS again so i reset it, and lo and behold it all showed up, but only until the next reboot. Back to bhe BIOS and just changed the ram from one speed to another and back again - RAM returns!

Erg.

Tagged junk.
Sunday, 19 November 2017, 13:22

I hate peecees

Well I was up till 3am fucking around with this bloody machine.

After verifying the hardware actually works it seems that the whole problem with my RAM not being found is the damn BIOS. I downloaded a bunch of BIOSs intending to try an older one and realised I hadn't installed the latest anyway. So I dropped than in and low and behold the memory came back. Yay.

So now I had that, I thought i'd try and get OpenCL working again. Ok, installed the latest (17.40) amdgpu-pro ... and fuck. Unsupported something or other in the kernel module. Sigh. I discovered that 17.30 did apparently work ... but it took a bit of digging to find a download link for it as AMD doesn't link to older releases (at this point i also found out midori has utterly shithouse network code. sigh). I finally found the right one (that wasn't corrupt), installed it and finally ...

Oh, back to 3.5G ram again. FAAARK.

At this point the power went out for the whole street so I had a shower using my phone's torch and went to bed.

Did some more digging when I got up (I was going to give up and say fuck it, but i've come this far), tried manually adding the ram using memmap, and finally confirmed the problem was the BIOS. So i tried an older one. That worked.

But only for a while, and then that broke as well. So trying the previous one ... groan.

Mabye it's time to cut my losses, it's already 1pm, the sun is out, heading for a lovely 31 degrees.

I also got rocm installed but i don't know if it works on this hardware, although at least the kernel is running ok so far.

Tagged junk, rants.
Saturday, 18 November 2017, 20:28

io scheduler, jfs, ssd

I didn't have much to do today and came across some articles about jfs and io schedulers and thought i'd run a few tests while polishing off a bottle of red (Noons Twleve Bells 2011). Actually i'd been waiting for a so-called "mate" to show up but he decided he was too busy to even let me know until after the day was over. Not like i've been suicidally depressed this week or anything.

The test I chose was to compile open jdk 9 which is a pretty i/o intensive and complex build.

My hardware is a Kaveri A10-7850K APU, "4G" of memory (sigh) on an ITX motherboard, and a Samsung SSD 840 EVO 250GB drive. For each test I blew away the build directory, re-ran configure, set the scheduler "echo foo > /sys/block/sda/queue/scheduler", and flushed the buffer caches "echo 3 > /proc/sys/vm/drop_caches" before running "time make images". I forced all cpu cores to a fixed 3.0Ghz using the performance scheduler.

At first I kept getting ICE's in the default compiler so I installed gcc-4.9 ... and got ICE's again. Inconsistently though, and we all know what ICE's in gcc means (it almost always means broken hardware, i.e. RAM). Sigh. It was afer a suspend-resume so that might've had something to do with it.

Well I rebooted and fudged around in the BIOS intending to play with the RAM clock but noticed I'd set the voltage too low. So what the hell I set it 1.60v and rebooted. And whattyaknow, suddenly I have 8G ram working again (for now), first time in a year. Fucking PCs.

Anyway so I ran the tests with each i/o scheduler on the filesystem and had no ICE's this time (which was dissapointing because it means the hardware isn't likely to be busted afterall, just temperamental). I used the default compiler. As it was a fresh reboot I ran builds from the same 80x24 xterm and the only other luser applications running beyond the panels and window manager were 1 other root exterm and an emacs to record the results.

cfq

real    10m39.440s
user    28m55.256s
sys     2m40.140s

deadline

real    10m36.500s
user    28m44.236s
sys     2m40.788s

noop

real    10m42.683s
user    28m43.960s
sys     2m41.036s

As expected from the articles i'd read, deadline (not the default in ubuntu!) is the best. But it's hardly a big deal. Some articles also suggested using noop for SSD storage but that is "clearly" worse (oddly that it increases sys time if it doesn't do anything). I only ran one test each in the order shown so it's only an illustrative result but TBH I'm just not that interested especially if the resutls are so close anyway. If there was something more significant I might care.

I guess i'll switch to deadline anyway, why not.

No doubt much of the compilation ran from buffer cache - infact this is over 2x faster than when I compiled it on Slackware64 a few days ago - at the time I only had 4G system ram (less the framebuffer) and a few fat apps running. But I also had different bios settings (slower ram speed) and btrfs rather than jfs.

As an aside I remember in the early days of Evolution (2000-2-x) when it took 45 minutes for a complete build on a desktop tower, and the code wasn't even very big at the time. That dell piece of crap had woefully shitful i/o. Header files really kill C compilation performance though.

Still openjdk is pretty big, and i'm using a pretty woeful CPU here as well. Steamroller, lol. Where on earth are the ryzen apu's amd??

notzed@minized:~/hg/jdk9u$ find . -type f \
  -a \( -name '*.java' -o -name '*.cpp' -o -name '*.c' \) \
   | xargs grep \; | wc -l
3063124

(some of the c and c++ is platform specific and not built but it's a good enough measure).

Tagged junk.
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