On Thu, Apr 22, 2021 at 07:47:29PM +0200, Matthias Schmidt wrote:
> I have a kernel with your patch running since several hours and
> noticed a regression. My usual "test case" is copying several large
> files from my file server via NFSv3 to my laptop. In the beginning the
> transfer rate was about 2-3M/s and after some time it dropped to around
> 50-300K/s and never recovered (transfer is now running for 2.5h).
>
> I have the following device in a Thinkpad T450s connect to a Fritzbox
> AP.
>
> iwm0 at pci2 dev 0 function 0 "Intel Dual Band Wireless-AC 8265" rev 0x78, msi
> iwm0: hw rev 0x230, fw ver 34.0.1, address
The patch doesn't actually change anything in the driver's receive path for
the 8265 chip. You might have seen a side-effect of something else that is
unrelated to the patch, such as the wifi channel suddently becoming very
busy with unrelated traffic. We should rule that out with a fair amount
of certainty before trying to debug the issue. So my question would be if
this problem is 100% repeatable with the patch and not at all repeatable
without the patch?
One possibility is that you've managed to trigger a problem in the receive
path of net80211 with A-MSDUs enabled. Such a bug would already have existed
but it would have been dormant since July 2019 when A-MSDUs were disabled.
For 8265 devices the entire patch boils down to this change so you could
simply revert all the other changes and try this much smaller patch instead
to test for this regression:
diff 804ff40445876fb6652323b00b9804f826133e70 /tmp/net80211
blob - a2de00f7bcdef99ced5d09da5e9b4bc8615156bd
file + ieee80211_input.c
--- ieee80211_input.c
+++ ieee80211_input.c
@@ -2758,7 +2758,7 @@ ieee80211_recv_addba_req(struct ieee80211com *ic, stru
ba->ba_params = (params & IEEE80211_ADDBA_BA_POLICY);
ba->ba_params |= ((ba->ba_winsize << IEEE80211_ADDBA_BUFSZ_SHIFT) |
(tid << IEEE80211_ADDBA_TID_SHIFT));
-#if 0
+#if 1
/* iwm(4) 9k and iwx(4) need more work before AMSDU can be enabled. */
ba->ba_params |= IEEE80211_ADDBA_AMSDU;
#endif
blob - 5bd45d993b558bac50a513c1c4422508d96f44ba
file + ieee80211_proto.c
--- ieee80211_proto.c
+++ ieee80211_proto.c
@@ -695,7 +695,7 @@ ieee80211_addba_request(struct ieee80211com *ic, struc
ba->ba_params =
(ba->ba_winsize << IEEE80211_ADDBA_BUFSZ_SHIFT) |
(tid << IEEE80211_ADDBA_TID_SHIFT);
-#if 0
+#if 1
/* iwm(4) 9k and iwx(4) need more work before AMSDU can be enabled. */
ba->ba_params |= IEEE80211_ADDBA_AMSDU;
#endif
