GA pilot reported a possible runway incursion. Pilot stated that due to cracks in the pavement; vegetation growing out of cracks; faded runway markings and an upward sloping taxiway the runway hold short line is not easily visible.

Narrative

PDK ground control initially cleared me to taxi from the FBO via taxiways B; E; cross RWY 16; to the runup area at the intersection of taxiways A; E and G. That runup area was very congested; to the point of being filled with aircraft; yet ground control continued to direct traffic to that area. The result was pressure to expedite the runup and exit the runup area to make room for other aircraft.I was in the northernmost corner of that runup area; facing south-southeast. The elevation at that particular location is 971 ft MSL. The surface slopes upward from there as you exit the runup area; rising to 972 ft - 973 ft MSL at that location on taxiway A; but then taxiway G slopes downward from taxiway A toward the departure end of RWY 21R to 969 ft MSL.The result of this topography is that from the northernmost corner of the runup area; the hold short line on taxiway G west of RWY 21R is not visible. It is obscured by the 'crest' of the surface. When the aircraft departs the northernmost position of this runup area; the nose points slightly upward because it is an upward slope; obscuring the hold short line on the downhill of the opposite side of the crest.As confirmed in the A/FD; RWY 21R is asphalt in only 'fair' condition. The runway markings are faded and cracked. The hold short line west of RWY 21R on taxiway G also is faded. All of those markings are further obscured by cracks in the surface with vegetation growing out of them.Upon completing my runup; I advised ground control and was directed by ground control to exit the runup area; proceed to the runway and to 'monitor' the tower. Due to the foregoing conditions; I was not able to see the hold-short line on taxiway G on the west side of RWY 21R until the aircraft proceeded beyond the crest of taxiway A and was almost on top of it; but I was able to stop before it; and before entering the runway environment. To the best of my knowledge; my aircraft was not beyond the hold short line; but I was closer to it than my usual practice. (I normally stop 8 ft - 10 ft before the hold short line.)As I was stopped and was holding short of RWY 21R; I contacted PDK tower to advise that I was 'holding short.' The tower controller chastised me for contacting him and told me that I was only supposed to 'monitor' him. I did not understand that; since I am not aware of any federal aviation regulation or other authority that prohibited me from contacting a tower with relevant operational information and for purposes of seeking assistance (i.e.; takeoff clearance). One to two minutes later; the tower instructed another aircraft that was on 2-3 mile final at pattern altitude to go around. The tower controller then told me that he thought I might have gone past the hold short line; and issued a telephone number to me with instructions to call upon arrival.The NACO Airport Diagram for PDK is unclear; and specifically; does not clearly identify as a hotspot the departure end of RWY 21R. All of the other hotspots have large circles or ovals around them. However; the oval that is drawn around the departure end of RWY 21R is small and does not go outside the edges of the runway. Therefore; the hotspot is not clearly or well depicted and does not provide adequate notice to a pilot who is being directed there by ATC.According to the A/FD; runway incursions are a known issue at this airport. And yet; ground control continued to funnel multiple aircraft to a highly congested area that is directly adjacent to a hotspot! The better practice would be to hold traffic on the ramps or at the FBOs; to better manage the flow of ground traffic and alleviate pressure to expedite pilot actions and simplify (rather than complicate) aircraft movement in this area of the field.Cracks in the pavement; vegetation growing out of cracks; and faded runway and taxiway markings should never be allowed to exist at a hotspot and near a hotspot.According to airport design standards; the hold short line issupposed to be 150 ft from the runway centerline. However; the hold short line on taxiway G west of RWY 21R is only 125 ft from the runway centerline. Not only is that a deviation from design standards; but it also is inconsistent with pilot expectations and operations at other airports. Yet; there is no publication that warns pilots or provides pilots with notice of this non-standard configuration. Given the fact that the hold short line is obscured by terrain/topography; faded markings; cracks in the pavement and vegetation; the hold short line for RWY 21R really should be placed at the beginning of taxiway G; where it can be better visualized by pilots.As for pilot actions; pilots should resist the pressure from ground control to expedite runups; and not hesitate to seek clarification; in this instance; clarification as to why I was not allowed or expected to initiate any communications with the tower.