I've recently installed OpenWRT on my Linksys, and I'm seeing pretty low download speeds.
I'm paying for a 1Gigabit connection (download) and according to speedtest, I'm sometimes getting 300/400 Mbit and sometimes 500/600 MBit (ethernet)
The situation with wifi (5ghz) is much worse, with no more than 220~.
The thing is, with the router my ISP is providing me (by force) speedtest.net does show the 950Mbit download over ethernet and 600~ over 5ghz.
I was also skeptical of speedtest accuracy, so I simply downloaded some big file from Steam, and the results were very close to speedtest.
I maxed out at 95mbps~ for my ISP provider router (ADBB-GT16005A) and 35~mbps for my Linksys running OpenWRT.
Last thing I checked was connecting my PC directly to ethernet port with no router in between to see if for some reason my ISP throttles down when it's receiving a DHCP request from unknown MAC, but speedtest.net showed results similar to ISP provided router.
Running OpenWrt 18.06.4 r7808-ef686b7292, not using QOS.
Same story here, just slightly worse (the ea8500 is ipq8064 based, while the nbg6817 would be ipq8065; additionally the ea8500 only uses a single CPU port to the switch, which limits the theoretical full-duplex bandwidth even further). In short, that's about the expected throughput range the ea8500 can master, you're pushing it beyond its abilities with 1 GBit/s WAN speed (if you can build OpenWrt from source kernel v4.19 might improve the situation a little, but not all the way).
Routing at 1 GBit/s linespeed still dabbles into enterprise territory, you need matching hardware for that, which basically boils down to x86_64 or mvebu.
Just as a small extension to the link above, servicing interrupts stemming from the wireless cards is also something that could be offloaded to the NSS/ NPU cores. Under high wireless throughput conditions, the ARMv7 cores have quite a lot to do dealing with this, work they have to do in addition to the actual routing/ NATing/ firewalling, etc., this is making the bottleneck at high WAN speeds even more pronounced.
Thank you very much for the quick response!!
I wasn't sure from your answer if stock firmware performs any better so I checked, and it seems like that's even worse. I guess I'll use the ISP router for the time being..
The OEM firmware should be able to use the NSS/ NPU cores for offloading, but this particular router has been designed by Linksys with the rather questionable decision to employ only a single CPU-port to the internal switch (all other known ipq806x devices use two, one exclusively for WAN, another for LAN), which basically halves your theoretical throughput at 1 GBit/s WAN speed to ~500 MBit/s (all data comes in from WAN, through the single CPU-port, back out to LAN via the very same CPU-port again --> effectively half-duplex).