On Sun, Nov 22, 2009 at 09:53:16PM -0600, Eric Sandeen wrote:
>
> Have you double-checked stack usage before & after the series, just
> in case all the folding-in increased some stack footprints?
The static stack footprints (on an x86) showed slight increases:
Before:
ext4_mb_free_blocks [vmlinux]: 124
ext4_ext_truncate [vmlinux]: 100
After applying the patch series:
ext4_free_blocks [vmlinux]: 136
ext4_ext_truncate [vmlinux]: 116
I was more concerned about the dynamic stack usage, so I ran xfstests
QA and then re-running test #74 (fstest), which seems to be the one
that uses the most stack. The results are not fully consistent (which
is why I manually re-ran #74 a few times to try to provoke the
smallest possible stack space left), but the worse case stack usage I
was able to find was:
Before:
fstest used greatest stack depth: 1084 bytes left
After applying the patch series:
fstest used greatest stack depth: 1024 bytes left
So it's slightly worse, but hopefully not enough to push us over the
edge. I think I can move some stack variables into inner blocks in
ext4_free_blocks() which should help, if we think this is a major
problem.
- Ted
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