RE: [Xen-devel] [PATCH 3/3] Replace slab.c with a very simpleallocator.

["Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>]

> > I think we want to ensure that the object returned is always
> > aligned to start on a L1 cache line boundary. I don't care that
> > we burn some memory as we don't have lots of small allocs.
> 
> If I may suggest, I'd prefer to put this in the hands of the caller,
> with an explicit alignment arg.  This simply falls out with this
> type-safe versions using __alignof__, and should neatly document this
> requirement, for example.

Hmm. I think pretty much everything we allocate is substantially biger
than a cache line, so there really isn't a whole lot of advantage in
doing this. We'd certainly have to go around sprinkling
__cacheline_aligned in a few more of our structure definitions to avoid
false sharing. BTW, I notice we use "__attribute__ ((aligned (X)))" in a
number of places as well as __alignof__. I presume they're the same
thing?

Out of interest, how do you extract information about such attributes
about structure definitions in a macro? 

> > Please could you adjust your patch having resync'ed from usntable.
> 
> Hmm, I hope that the bk snapshot is close enough.

The snapshot from last night should be OK (Keir removed _xmalloc late
last night GMT, so make sure you have this).

Thanks,
Ian


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