Re: Freezing bug in all kernels greater than 2.4.5-ac13 *AND*

[Marcelo Tosatti]

On Wed, 27 Jun 2001 [e-mail] wrote:

> I decided, for the hell of it, to test the pre series as I've been
> nudged by many people to try it in favor of the ac kernel series that
> I've been having problems with. Well, it turns out I have ran into
> exactly the same problem I had with the ac kernel series, which quite
> frankly is surprising the hell out of me.
> 
> To make the kernel freeze/slow down to a crawl with affected kernels on
> my machine I do this test:
> 
> Load X (This fills up my ram and causes me to swap a bit)
> run a rxvt and su to root (proboably unnecessary)
> du /
> 
> Now, somewhere in this test I start swapping a little bit, nothing
> big... then BAM. hard disk, mouse, keyboard, all completely and utterly
> stop. Video continues to work, but my cpu's load goes absolutely INSANE.
> (If it recovers, gkrellm generally says I've gotten a loadavg somewhere
> between 3-20, depending on how long it was stuck) This can last for
> seconds (usually) minutes (once) or it can simply get worse and hang the
> machine (many, many many times)
> 
> When it recovers from this, I generally see a MASSIVE write to swap,
> (I'm using gkrellm to monitor it) and the system continues on as if
> nothing happened - until, of course, this happens again. A kernel
> compile can cause it. a rm -R of a large directory can cause it. Loading
> a large application can cause it.
> 
> On some kernels this is more noticable than others - ac15 does it the
> worst, although pre3 rivals it, and the symptoms are different on
> ac17/18 - it'll simply freeze randomly and with no recovery instead of
> sometimes freezing or sometimes slowing down to a crawl and recovering
> or freezing. (Which is worse? You decide.)
> 
> Now, as before, I tested this with swap and without swap. With swap, I
> get the hangs/freezes in all the affected kernels. Without swap, I
> don't. Nada.
> 
> Now, the big question of the day folks: What changed between 2.4.6-pre2
> and 2.4.6-pre3 that ALSO changed between 2.4.5-ac13 and 2.4.5-ac14 - and
> now, what part of those patches were the VM? Anyone? I don't see in
> 2.4.6-pre3 what changed that was part of the VM... So I am trying to
> narrow it down a bit :)
> 
> This bug is driving me slightly nuts, so I want it dead. Anyone got a
> exterminator handy? =)

Rik's page_launder() changes. 

> 
> Refer to my previous post with this subject for my original description
> of this problem. It's still there in ac18, though I've not tested 19
> (Some have said it's not likely to have been fixed, and I've been
> regress testing 2.4.6pre's today.)
> 
> Subject: Possible freezing bug located after ac13
> 
> Let me know if I can provide any additional information that will help
> nail this bug to the wall. (I want to torture it. =)