Re: dentry bloat.

[Linus Torvalds]

On Sat, 8 May 2004, Andrew Morton wrote:
> 
> I think that'll crash.  DNAME_INLINE_LEN_MIN is the *minimum* storage in
> the dentry.  The actual storage is assumed to be DNAME_INLINE_LEN and the
> patch doesn't change that value.

It doesn't need to, the value is correct.

> The calculation of DNAME_INLINE_LEN assumes that slab padded the dentry out
> to the next cacheline.

No it doesn't. It's just:

	#define DNAME_INLINE_LEN (sizeof(struct dentry)-offsetof(struct dentry,d_iname))

which is always right. 

It used to assume the padding because of the "____cacheline_aligned" on 
the struct dentry, which obviously also padded out the "sizeof()". But 
since I removed that, DNAME_INLINE_LEN is still correct.

NOTE! It's absolutely true that DNAME_INLINE_LEN may still be different 
from DNAME_INLINE_LEN_MIN. In particular, if something inside the struct 
makes the alignment of "struct dentry" be bigger than the offset of the 
last field, then DNAME_INLINE_LEN will be different from (bigger than) 
DNAME_INLINE_LEN.

It's just that with current architectures, I don't believe that will 
happen in practice. But I left it as-is, because at least in theory it 
could happen.

		Linus
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/