I'm not going to get into the whole feudalism debate here, but know that there are a lot of things that term can mean and it's a difficult one to use precisely. The early Middle Ages, which is usually seen as a "pre-feudal" period by those who still use the term, saw European armies almost exclusively raised by mass levy of the free (and armed) population, while the high and late Middle Ages, often thought of as the height of feudalism, witnessed decreasing use of the levy system and more outright hiring of troops and reliance on nobles' retinues. But no, knights were generally a smallish portion of any army: a quarter, a fifth, perhaps less, and that proportion decreased over time as more and more untitled men-at-arms assumed the knights' traditional military function.

It's important to remember that part of why we fixate so much on the levy is because we have tangible proof for it in the sources. Medieval military recruitment is a murky subject precisely because contemporary writers didn't really care about the infantry or where they came from; they were concerned with the knightly class and its doings, not the PBI. It is exceedingly likely that even in places that maintained the "peasant levy," noblemen kept armed men around them in peacetime who then followed them to war. There's also evidence for paid soldiers serving in castle garrisons as early as the 11th century, and I suspect soldiers were often hired on a short-term basis before campaigns, but the evidence just isn't there for it.