> Hi > > On Thu, Jun 13, 2019 at 10:26:38AM +0200, Lorenzo Bianconi wrote: > > [...] > > > > > I looked at intel wifi drivers and this is handled by amsdu_size module > > > parameter, supported values are 4k, 8k and 12k. RX allocation size and > > > proper values in vht_cap & ht_cap are set accordingly. Assuming (some) > > > mt76 HW and FW can handle bigger AMSDUs I think we should do similar > > > thing. > > > > > > Otherwise looks for me, we just waste memory and have not needed code > > > for no true reason. > > > > > > > space needed for skb_shared_info is 320B on a x86_64 device > > > > > > Uhh, I haven't expected that sk_shared_info() is that big, so indeed > > > build_skb > > > could not used and 128B copy fallback will be necessary. > > > > Hi Stanislaw, > > > > reviewing the original patch I think we can't trigger any IOMMU bug since > > the > > usb buffer length is actually 2048 and not 2048 + skb_shared_info_size: > > I'm concerned about alignment and crossing pages boundaries. If you > allocate via page_frag_alloc() buffers, except first one, will have > 'not natural' alignment and every second will be spanned across > two pages.
ack, so I think the second approach will be safer (using roundup instead of rounddown :)) Regards, Lorenzo > > Stanislaw >
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