Several studies have found that ingesting carbs before your workout can help improve performance, especially in endurance events. Shoot for 30-60 grams within an hour before your workout to maximize the effect. If you are keto-adapted, large amounts of pre-workout carbs will probably not be best. Stick to a high-fat meal before training for a similar effect. If you don’t train for more than an hour at a time, carbohydrate availability is not a limiting factor for your performance and you probably don’t need a large amount of carbs before your workout.
Reference: Neufer, P. D., Costill, D. L., Flynn, M. G., Kirwan, J. P., Mitchell, J. B., & Houmard, J. (1987). Improvements in exercise performance: effects of carbohydrate feedings and diet. Journal of Applied Physiology, 62(3), 983-988.