[Bug 1169996] TP-Link UE300 ethernet adpater (r8152) very slow on receive since kernel 5.4
https://bugzilla.suse.com/show_bug.cgi?id=1169996
https://bugzilla.suse.com/show_bug.cgi?id=1169996#c1
Shung-Hsi Yu
r8152: limit the RX buffer size of RTL8153A for USB 2.0
If the USB host controller is EHCI, the throughput is reduced from 300Mb/s to 60Mb/s, when the rx buffer size is modified from 16K to 32K.
According to the EHCI spec, the maximum size of the qTD is 20K. Therefore, when the driver uses more than 20K buffer, the latency time of EHCI would be increased. And, it let the RTL8153A get worse throughput.
However, the driver uses alloc_pages() for rx buffer, so I limit the rx buffer to 16K rather than 20K.
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