Mark Hemment wrote:
>
> > > Hmm, no that note, seen the L1 line size defined for a Pentium IIII?
> > > 128 bytes!! (CONFIG_X86_L1_CACHE_SHIFT of 7). That is probably going to
> > > waste a lot of space for small objects.
> > >
> > No, it doesn't:
> > HWCACHE_ALIGN means "do not cross a cache line boundary".
>
> Ah, I broke my code!!!!! :(
>
> In my original slab, the code to do "packing" of objects into a single
> cache line was #if-def'ed out for SMP to avoid the possibility of
> false-sharing between objects. Not a large possibility, but it exists.
>
But then you need SMP_CACHE_BYTES, not L1_CACHE_BYTES.
And 128 byte aligning the 32-byte kmalloc cache wastes too much memory
;-)
If the caller of kmem_cache_create really wants do avoid false sharing
he could set align to SMP_CACHE_BYTES. (e.g. for some per-cpu data
structures)
> > Even if the hot zone is larger than the default offset, is there any advantage
> > of increasing the colour offset beyond the alignment?
> >
> > I don't see an advantage.
>
> I do, but like you, I don't have any data to prove my point.
> Time to get profiling?
>
How? You've already noticed that noone in the linux kernel uses offset.
--
Manfred
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
