Messages in this thread | | | Date | Thu, 18 May 2023 15:26:15 +0200 | Subject | Re: [PATCH net-next 06/11] net: page_pool: avoid calling no-op externals when possible | From | Alexander Lobakin <> |
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From: Christoph Hellwig <hch@lst.de> Date: Wed, 17 May 2023 10:14:58 +0200
> So while this looks ok, Eric Dumazet had looked into some optimization > for this touching the core code, and promised me to come up with an > even better version a while ago. Eric, what's the state of your > optimizations for no-op DMA syncs? >
Hmm, his last proposals were for avoiding indirect calls when IOMMU is on, but in fact we don't need to synchronize stuff -- DMA IOMMU on x86_64 also usually doesn't synchronize anything, but you don't know that prior to doing an indirect call and dma_need_sync() won't help. I was thinking of adding .dma_need_sync() callback to DMA ops, which could also be called once only on page allocation, like in this patch.
Also want to hear how it goes for Eric :)
Thanks, Olek
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