From: Johannes Berg <johannes@sipsolutions.net> To: "Toke Høiland-Jørgensen" <toke@redhat.com>, "Kan Yan" <kyan@google.com> Cc: linux-wireless@vger.kernel.org, make-wifi-fast@lists.bufferbloat.net, ath10k@lists.infradead.org, John Crispin <john@phrozen.org>, Lorenzo Bianconi <lorenzo@kernel.org>, Felix Fietkau <nbd@nbd.name>, Rajkumar Manoharan <rmanohar@codeaurora.org>, Kevin Hayes <kevinhayes@google.com> Subject: Re: [PATCH v2 1/4] mac80211: Rearrange ieee80211_tx_info to make room for tx_time_est Date: Fri, 18 Oct 2019 14:35:40 +0200 [thread overview] Message-ID: <4bc17c32337888a57a78a0e2c874abd462faef21.camel@sipsolutions.net> (raw) In-Reply-To: <87sgnqe4wg.fsf@toke.dk> On Fri, 2019-10-18 at 12:15 +0200, Toke Høiland-Jørgensen wrote: > Kan Yan <kyan@google.com> writes: > > > The "tx_time_est" field, shared by control and status, is not able to > > survive until the skb returns to the mac80211 layer in some > > architectures. The same space is defined as driver_data and some > > wireless drivers use it for other purposes, as the cb in the sk_buff > > is free to be used by any layer. > > > > In the case of ath10k, the tx_time_est get clobbered by > > struct ath10k_skb_cb { > > dma_addr_t paddr; > > u8 flags; > > u8 eid; > > u16 msdu_id; > > u16 airtime_est; > > struct ieee80211_vif *vif; > > struct ieee80211_txq *txq; > > } __packed; > > Ah, bugger, of course the driver that actually needs this is using the > full driver_data space :P Looks like you could shrink *this* fairly easily though. E.g. most likely vif == txq->vif unless txq==NULL, so it's down to 22 bytes plus a bit/flag for knowing whether the pointer is a vif directly (if no TXQ) or a TXQ. > > Do you think shrink driver_data by 2 bytes and use that space for > > tx_time_est to make it persistent across mac80211 and wireless driver > > layer an acceptable solution? > > Hmm, the driver_data field is defined as an array of pointers, so we can > only shrink it in increments of sizeof(void *). I think it may be > feasible to shrink it (as in, I don't think any drivers are actually > using the full 40 bytes), It doesn't have to be defined like that, just was most convenient as driers were using pointers there. > but doing this in a way that will gain us a > 2-byte space that is also usable in the case driver_data is *not* used > (i.e., it needs be able to align with a field in .control and .status as > well) would require some serious surgery of the whole ieee80211_tx_info... Yeah, good point, this doesn't help at all ... johannes
WARNING: multiple messages have this Message-ID (diff)
From: Johannes Berg <johannes@sipsolutions.net> To: "Toke Høiland-Jørgensen" <toke@redhat.com>, "Kan Yan" <kyan@google.com> Cc: Rajkumar Manoharan <rmanohar@codeaurora.org>, Kevin Hayes <kevinhayes@google.com>, make-wifi-fast@lists.bufferbloat.net, linux-wireless@vger.kernel.org, ath10k@lists.infradead.org, John Crispin <john@phrozen.org>, Lorenzo Bianconi <lorenzo@kernel.org>, Felix Fietkau <nbd@nbd.name> Subject: Re: [PATCH v2 1/4] mac80211: Rearrange ieee80211_tx_info to make room for tx_time_est Date: Fri, 18 Oct 2019 14:35:40 +0200 [thread overview] Message-ID: <4bc17c32337888a57a78a0e2c874abd462faef21.camel@sipsolutions.net> (raw) In-Reply-To: <87sgnqe4wg.fsf@toke.dk> On Fri, 2019-10-18 at 12:15 +0200, Toke Høiland-Jørgensen wrote: > Kan Yan <kyan@google.com> writes: > > > The "tx_time_est" field, shared by control and status, is not able to > > survive until the skb returns to the mac80211 layer in some > > architectures. The same space is defined as driver_data and some > > wireless drivers use it for other purposes, as the cb in the sk_buff > > is free to be used by any layer. > > > > In the case of ath10k, the tx_time_est get clobbered by > > struct ath10k_skb_cb { > > dma_addr_t paddr; > > u8 flags; > > u8 eid; > > u16 msdu_id; > > u16 airtime_est; > > struct ieee80211_vif *vif; > > struct ieee80211_txq *txq; > > } __packed; > > Ah, bugger, of course the driver that actually needs this is using the > full driver_data space :P Looks like you could shrink *this* fairly easily though. E.g. most likely vif == txq->vif unless txq==NULL, so it's down to 22 bytes plus a bit/flag for knowing whether the pointer is a vif directly (if no TXQ) or a TXQ. > > Do you think shrink driver_data by 2 bytes and use that space for > > tx_time_est to make it persistent across mac80211 and wireless driver > > layer an acceptable solution? > > Hmm, the driver_data field is defined as an array of pointers, so we can > only shrink it in increments of sizeof(void *). I think it may be > feasible to shrink it (as in, I don't think any drivers are actually > using the full 40 bytes), It doesn't have to be defined like that, just was most convenient as driers were using pointers there. > but doing this in a way that will gain us a > 2-byte space that is also usable in the case driver_data is *not* used > (i.e., it needs be able to align with a field in .control and .status as > well) would require some serious surgery of the whole ieee80211_tx_info... Yeah, good point, this doesn't help at all ... johannes _______________________________________________ ath10k mailing list ath10k@lists.infradead.org http://lists.infradead.org/mailman/listinfo/ath10k
next prev parent reply other threads:[~2019-10-18 12:35 UTC|newest] Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-10-15 17:18 [PATCH v2 0/4] Add Airtime Queue Limits (AQL) to mac80211 Toke Høiland-Jørgensen 2019-10-15 17:18 ` Toke Høiland-Jørgensen 2019-10-15 17:18 ` [PATCH v2 1/4] mac80211: Rearrange ieee80211_tx_info to make room for tx_time_est Toke Høiland-Jørgensen 2019-10-15 17:18 ` Toke Høiland-Jørgensen 2019-10-18 0:50 ` Kan Yan 2019-10-18 0:50 ` Kan Yan 2019-10-18 10:15 ` Toke Høiland-Jørgensen 2019-10-18 10:15 ` Toke Høiland-Jørgensen 2019-10-18 12:21 ` Johannes Berg 2019-10-18 12:21 ` Johannes Berg 2019-10-18 13:31 ` Toke Høiland-Jørgensen 2019-10-18 13:31 ` Toke Høiland-Jørgensen 2019-10-18 13:48 ` Johannes Berg 2019-10-18 13:48 ` Johannes Berg 2019-10-18 14:01 ` Toke Høiland-Jørgensen 2019-10-18 14:01 ` Toke Høiland-Jørgensen 2019-10-18 14:07 ` Johannes Berg 2019-10-18 14:07 ` Johannes Berg 2019-10-18 14:22 ` Toke Høiland-Jørgensen 2019-10-18 14:22 ` Toke Høiland-Jørgensen 2019-10-18 14:14 ` Johannes Berg 2019-10-18 14:14 ` Johannes Berg 2019-10-18 14:30 ` Toke Høiland-Jørgensen 2019-10-18 14:30 ` Toke Høiland-Jørgensen 2019-10-18 12:35 ` Johannes Berg [this message] 2019-10-18 12:35 ` Johannes Berg 2019-10-18 13:01 ` Ben Greear 2019-10-18 13:01 ` Ben Greear 2019-10-15 17:18 ` [PATCH v2 2/4] mac80211: Import airtime calculation code from mt76 Toke Høiland-Jørgensen 2019-10-15 17:18 ` Toke Høiland-Jørgensen 2019-10-15 17:19 ` [PATCH v2 3/4] mac80211: Implement Airtime-based Queue Limit (AQL) Toke Høiland-Jørgensen 2019-10-15 17:19 ` Toke Høiland-Jørgensen 2019-10-15 17:19 ` [PATCH v2 4/4] mac80211: Use Airtime-based Queue Limits (AQL) on packet dequeue Toke Høiland-Jørgensen 2019-10-15 17:19 ` Toke Høiland-Jørgensen 2019-10-17 0:33 ` Kan Yan 2019-10-17 0:33 ` Kan Yan 2019-10-17 9:44 ` Toke Høiland-Jørgensen 2019-10-17 9:44 ` Toke Høiland-Jørgensen 2019-10-17 9:57 ` [Make-wifi-fast] " Sebastian Moeller 2019-10-17 9:57 ` Sebastian Moeller 2019-10-17 10:24 ` Toke Høiland-Jørgensen 2019-10-17 10:24 ` Toke Høiland-Jørgensen 2019-10-17 10:25 ` Sebastian Moeller 2019-10-17 10:25 ` Sebastian Moeller 2019-10-18 1:11 ` Kan Yan 2019-10-18 1:11 ` Kan Yan 2019-10-18 14:15 ` Johannes Berg 2019-10-18 14:15 ` Johannes Berg
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