Analysing freezes/latency in linux

PhantomBeaker · 26-05-2010 03:51PM #1

Hey all,

I've recently upgraded my desktop to a shiny Core i7 920 sitting on an Asus P6T (standard) motherboard, with 12G of ram, and 2x1TB harddrives (don't have the model to hand) with windows on sda, and linux Mint 8 (64-bit) sitting on some logical partitions on sdb.

Now, I've noticed some sporadic freezes. If I'm doing updating the system, it will take over 10 seconds to load a terminal if I click on the icon. I also notice a few "thinking" phases on firefox sessions (hover the mouse over a link, and the icon doesn't change, nor does it respond to clicks) that have no javascript in them.

When I tried this on my old Core 2 Duo system with 2G of ram, it worked smoothly. No latency at all.

If I run any cpu-intensive benchmarks, I notice no performance degradation, and seem to get good results. So I doubt it's CPU-bound.

Also, I don't notice anything like this on windows 7 on the same system.

However, after that, I'm pretty much out of ideas for analysing this problem. I may try the underlying version of ubuntu to see if it's mint or not.

So what else should I be looking at? I realise that it's an old release now (mint 9 just came around this month) so I should look at that, but I'd like to have some level of confidence that I'm not going to just hit this issue again. And it'd be handy to figure out if there's an underlying hardware misconfiguration.

Any pointers would be appreciated.

Thanks,
Aoife

BopNiblets · 26-05-2010 11:42PM

Run firefox in safemode via the terminal may show up some errors, or try a different browser (Chrome is out of beta on Linux recently I believe).
Also check out the Log File Viewer (type it in the main menu), just open it up and any logs that go bold in the left side list are getting entries added at the bottom and could show any problems.

Mint 9 is pretty cool btw.

PhantomBeaker · 27-05-2010 01:02AM

See, the problem isn't just firefox. It's when I'm doing things like an apt-get upgrade, and it takes several seconds to get a terminal window open, so it's inclining me to think it's not just firefox that's having a problem.

Someone recommended disabling HT, which I tried, but had no joy with. I've seen it in 32 and 64 bit versions.

What I'd like to do is, to verify if it's I/O, is to hammer the disk, or some other partition a bit and see if I get the same problems. (The reason I'm half-thinking it's disk has to do with the fact that it worked fine on the livecd)

Is there anything other than the basic benchmarks which come with the distro to test for potential bottlenecks?

Anyway, I'll give the log viewer a try. (I'm guessing it's like a user friendly dmesg?)

Thanks,
Aoife

loldog · 27-05-2010 02:57AM

Try re-profiling. When you get to the Grub menu, press e on the kernel you normally boot, then you may have to press e again I can't remember. But find the line that has "quiet splash" at the end and add the word profile.

Then I think it's Ctrl + X to boot up. Read more about it here:

http://ubuntuforums.org/showthread.php?t=254263

It's made a huge difference for me in the amount of RAM being used.

.

PhantomBeaker · 27-05-2010 10:46AM

@loldog: Thanks. I just read the link, and it looks like there are enough reasons I'd want to try it (like picking a non-default FS at install time). Thanks, I'll have a look at that when I get home.

loldog · 27-05-2010 11:47AM

PhantomBeaker wrote: »

@loldog: Thanks. I just read the link, and it looks like there are enough reasons I'd want to try it (like picking a non-default FS at install time). Thanks, I'll have a look at that when I get home.

The link is a little outdated, it refer to legacy Grub but you will be able to work out what to do in Grub 2, it's quite similar.

.

PhantomBeaker · 27-05-2010 01:48PM

Funnily enough, due to a grub2 performance regression (See https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/420933?comments=all - basically a lot of slowness when you have your /boot partition on your secondary hard disk, and grub2 on the MBR of your primary disk... as you can imagine, this was not a good start to the ubuntu/mint experience on my new desktop), I've been very seriously considering dropping down to grub1 anyway. There again, that bug should be fixed and available in Lucid, so I may not have to (but I'm not on ext4, so I can do it if I really need to).

PhantomBeaker · 27-05-2010 10:51PM

Cheers, between the log viewer and readahead, I have a bit to chew on. I'm still seeing latency, but I think I know where to start looking for data.

I tried regenerating the pack file for ureadahead (with the profile option), but when I took out the fbsplash, I noticed that all the ureadahead processes were exiting with a status of 4... and I need to check out if ureadahead is meant to be running as a service in normal execution (as in normal out-of-the-box init 5) or not. Actually, does anyone know this should be the case or not?

Also, I'm noticing some interesting activity in /var/log/pm-powersave.log - I'm echoing some stuff into the file to see if that log is rotated at every boot or not - seriously, what is it with these logs not having freaking timestamps... what sort of analysis do people expect you to be able to do, when you can't put together a decent timeline. It's just pm-powersave.log and udev by the looks of things, but I would have thought it would be important for them to carry that sort of thing. Sorry, rant over; I just... care... about logs.

Anyway, thanks for the help, I've at least got a little bit to chew on, as I said. (also, it's sad that I'm this out of practise with linux).

Thanks,
Aoife

Analysing freezes/latency in linux

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