Messages in this thread | | | Date | Fri, 31 Mar 2006 11:43:15 +0200 | From | Adrian Bunk <> | Subject | Re: Save 320K on production machines? |
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On Thu, Mar 30, 2006 at 01:34:07PM -0800, Linda Walsh wrote: >... > If I "doubled" my stack back to 8K, that would lower the "random > probability" of hitting a stack limit, but right now, it seems like > amount of stack "needed" is nearly guesswork. Sigh. Having my > kernel fairly static and minimalistic (no unused modules; no loadable > modules, etc) I might only "need" 3K.
Things like unused modules or loadable module support should have more or less zero impact on stack usage.
> 1) It would be nice if a "stack usage" option could be turned on > that would do some sort of run-time bounds checking that could > display the max-stack used "so far" in "/proc".
The -rt kernel contains something like this.
> 2) How difficult would it be to place kernel stack in a "pageable" pool > where the limit of valid data in a 4K page is only 3.5K - then > when a kernel routine tries to exceed the stack boundary, it takes a > page fault where a "note" could be logged that more stack was "needed", > then automatically map another 4K page into the stack and return to > interrupted routine. > > It sounds a bit strange -- the kernel having to call another part of > the kernel to handle a pagefault within the kernel, but perhaps there > could be another level of "partitioning" w/in kernel space that would > allow the non-paging part of the kernel to be paged in/out in a similar > way to user code. >...
This has been discussed to death, and the consensus was that code resulting in a too high stack usage should be fixed.
If you find any stack problems with 4k stacks and the automatically enabled unit-at-a-time when using gcc 4.x in kernel 2.6.16-mm2, please send a bug report.
Regarding unit-at-a-time with gcc 3.x, it works most time for most people, but it's completely unsupported. If you want to use unit-at-a-time on i386, please use gcc 4.x.
> -l
cu Adrian
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