From: Bjørn Mork <bjorn@xxxxxxx> Date: Wed, 23 Jan 2013 11:57:02 +0100 > Reverting 328d7b8 and instead adding an exception for the > Sierra Wireless MC7710. > > commit 328d7b8 (net: cdc_mbim: send ZLP after max sized NTBs) > added a workaround for an issue observed on one specific device. > Concerns were raised that this workaround adds a performance > penalty to all devices based on questionable, if not buggy, > behaviour of a single device: > > "If you add ZLP for NTBs of dwNtbOutMaxSize, you are heavily affecting CPU > load, increasing interrupt load by factor of 2 in high load traffic > scenario and possibly decreasing throughput for all other devices > which behaves correctly." > > "The idea of NCM was to avoid extra ZLPs. If your transfer is exactly > dwNtbOutMaxSize, it's known, you can submit such request on the receiver > side and you do not need any EOT indicatation, so the frametime can be > used for useful data." > > Adding a device specific exception to prevent the workaround from > affecting well behaved devices. > > The assumption here is that needing a ZLP is truly an *exception*. > We do not yet have enough data to verify this. The generic > workaround in commit 328d7b8 should be considered acceptable despite > the performance penalty if the exception list becomes a maintainance > hassle. > > Cc: Alexey ORISHKO <alexey.orishko@xxxxxxxxxxxxxx> > Cc: Yauheni Kaliuta <y.kaliuta@xxxxxxxxx> > Signed-off-by: Bjørn Mork <bjorn@xxxxxxx> Applied. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
