Messages in this thread | | | Date | Fri, 6 Aug 2004 09:58:35 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: Possible dcache BUG |
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On Fri, 6 Aug 2004, Gene Heskett wrote: > > Linus, Andrew, should I apply this patch too at the next remake?
Might be worth it, but it's more important to see any oops at all, or lack of oopses..
> FWIW, I'm still up (20:38) this morning, and showing plenty (127+ > megs) of free memory. No crash, no odd log (other than samba > squawking about some option thats been changed & I haven't fixed the > smb.conf) so far. > > I'm beginning to like this test patch, Linus, thanks :)
If the only thing you have done is add the list_del_init() debugging patch, then the only thing that has changed is really the access patterns to uncached memory.
The original list_del_init() tries to only do a few single _writes_ to the dentries around it. The added debugging will do _reads_ (and thus bring it into the cache) of the dentry pointers of the dentries around it.
If that change makes a real difference, I really only see two possibilities: - there really is a prefetch bug (or possibly, there's a bug in our prefetch fixup code, and the known prefetch bug just triggers the problem indirectly) - it just changes the timing enough that whatever bug you hit went away.
Now, Chris Shoemaker reported dentry problems on a intel CPU and said that wli had seen something too, but I'm wondering whether Chris and wli might have been seeing the knfsd/xfs-related dentry bug that I found yesterday. So I think the prefetch theory is still alive, but we should check with Chris. Chris?
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