I Instruct Shaolin Kempo.
We have many techniques which deal with defending against the blade.
To inject some level of reality to the training, when we are in the blade defense cycle, I take one day, invite everyone to wear their ' civies ', and I use a waterbased red marker to paint the edges and points of the blades.
At the end of the session everyone including myself has a greater realization of the truism that if you pklay with knives you WILL be cut, as the red marks are abundant. There is almost no way to prevent reverse cut with a double edged blade, and if a person has even the slightest training in real knife fighting situations, they find that the blade isnt presented for any length of time, and when one factors in the accumulated shcok factors of blood loss due to alot of cuts, let alone the deadly shock of a stabbing wound, the best advise I can give my students is that ' unarmed defense against a knife ( or sword ) is the equvalent of an oxymoron '.
Run like the wind is the best bet. If you cant run, realize that you can save your life with training, but that means creating a door and going through it as fast as it is presented.