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Subject: Re: [PATCH v3 wireless-drivers 1/3] mt76: usb: fix rx A-MSDU support
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Lorenzo Bianconi <lorenzo.bianconi@redhat.com>,
        Stanislaw Gruszka <sgruszka@redhat.com>
Cc:     Lorenzo Bianconi <lorenzo@kernel.org>, kvalo@codeaurora.org,
        linux-wireless@vger.kernel.org, nbd@nbd.name
Date:   Fri, 14 Jun 2019 12:20:59 +0200
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On Fri, 2019-06-14 at 12:11 +0200, Lorenzo Bianconi wrote:

> Looking at __ieee80211_amsdu_copy() now I got why other drivers copy hdrlen +
> 8, thx :)
> In our case reuse_frag is true in __ieee80211_amsdu_copy, so we will end up
> copying 32B + ether_len. Anyway I think 32 is a little bit too low and we could get
> better performances increasing it a little bit.
> A typical use case (e.g IPv6 + TCP):
> 
> IPv6 = 40B, TCP = 32B --> so 72B..I guess 128B is a good value :)
> @Felix, Johannes: what do you think?

I think while we might *allocate* more, I don't think we should *copy*
more, since then the TCP payload will no longer be in pages.

It'd probably be better to implement leaving enough tailroom (allocate
128), but copying nothing, unless the *entire* packet fits.

johannes