[ath9k-devel] ath9k monitor mode injection packet delay

[Cesar <caesargo@163.com>]

Hello all,
We?ve recently tried to test packet injection performace in ath9k monitor mode. We set 2 laptops in monitor mode , PC 1 send a 500 Byte packets out, and PC 2 return a 500 Bytes packet back at once when it receives the packet of PC 1. Then we measured the RTT time and found it's about 1000us !!!


Test environment:
NIC: AR9287
driver: ath9k
system: ubuntu 14.04 with kernel 3.14.57
send rate : at a fixed rate 54Mb




We tried to send packets as "low" as possible in driver stack, and we're sure that we disabled the CCA and backoff using flags below:

AR_DIAG_FORCE_CH_IDLE_HIGH
AR_DIAG_IGNORE_VIRT_CS
AR_D_GBL_IFS_MISC_IGNORE_BACKOFF


besides we change the aifs to 1 and cwmin cwmax to 0 in ath_txq_setup to ensure there's no backoff. we even put our laptaps to a underground garage where channel is almost clean.But the test results is still about 1000us....


We've been stucked for serveral months, Any suggestion?
Any feedback welcome...
Thnkz in advance!!!


Cesar


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