Messages in this thread | | | Date | Sat, 17 Dec 2005 21:52:38 +0100 | From | Adrian Bunk <> | Subject | Re: [2.6 patch] i386: always use 4k stacks |
| |
On Sat, Dec 17, 2005 at 06:44:07PM +0100, Andi Kleen wrote: > Kyle Moffett <mrmacman_g4@mac.com> writes: > > > On Dec 16, 2005, at 10:35, Diego Calleja wrote: > > > I know, but there's too much resistance to the "pure" 4kb patch. > > > > I have yet to see any resistance to the 4Kb patch this time around > > that was not "*whine* don't break my ndiswrapper plz". > > My comment from last time about the missing safety net still applies 100%. > > Kernel code is getting more complex all the time and running with > very tight stack is just risky.
My patch reduces it from roughly 6kB to 4kB.
I'm with you that we need a safety net, but I don't see a problem with this being between 3kB and 4kB. The goal should be to _never_ use more than 3kB stack having a 1kB safety net.
And in my experience, many stack problems don't come from code getting more complex but from people allocating 1kB structs or arrays of > 2k chars on the stack. In these cases, the code has to be fixed and "make checkstack" makes it easy to find such cases.
And as a data point, my count of bug reports for problems with in-kernel code with 4k stacks after Neil's patch went into -mm is still at 0.
> > The point is to force it in -mm so most people can't just disable it > > because it fixes their problem. We want 8k stacks to go away, and > > Who is we? And why? > > About the only half way credible arguments I've seen for it were: > > - "it might reduce stalls in the VM with order 1". Didn't quite > convince me because there were no numbers presented and at least on > x86-64 I've never noticed or got reported significant stalls because > of this. > > - "it allows more threads for 32bit which might run out of lowmem" - i > think everybody agrees that the 10k threads case is not really > something to encourage. And even when you want to add it then only a factor > two increase (which this patch brings) is not really too helpful. >...
Unfortunately, "is not really something to encourage" doesn'a make "happens in real-life applications" impossible...
Reducing the stack by one third brings a factor two reduction in the memory usage of threads - I wouldn't say this sounds too bad.
> -Andi
cu Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out of the darkness. There had been need of rain for many days. "Only a promise," Lao Er said. Pearl S. Buck - Dragon Seed
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |