[ovs-dev] [non-NORMAL learning 2/3] tag: Be more precise about choosing tags to add, in tag_set_add().

Jesse Gross jesse at nicira.com
Thu Aug 5 17:41:28 UTC 2010

On Wed, Aug 4, 2010 at 10:27 AM, Ben Pfaff <blp at nicira.com> wrote:

> There is no need to add "tag" values with only a single bit set, but until
> now tag_set_add() would do so anyhow.  (That is not a bug, it is only a
> possible performance loss.)  It is likely that no existing caller ever
> tries to do this, but an upcoming commit will start creating 1-bit tags
> and thus introduce the possibility, so it seems like a good idea to avoid
> the problem before it starts.

I don't like the concept of 1 bit tags (see the response to the next patch
in this series) so rather than try to handle them I would prefer that we
just ensure that they never occur.

> It is also not necessary to add a "tag" if all of the bits in it are
> already present in some member of the set, so add that optimization too.

This part looks fine.
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