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Date: Mon, 17 Aug 2009 17:57:00 -0700 (PDT) From: David Miller <davem@...emloft.net> To: ron.mercer@...gic.com Cc: netdev@...r.kernel.org Subject: Re: [RFC net-next PATCH 0/4] qlge: Performance changes for qlge. From: Ron Mercer <ron.mercer@...gic.com> Date: Mon, 17 Aug 2009 14:08:45 -0700 > 1) Do TX completions in send path (with cleaner timer). You should really do them in NAPI context. When you do them from hardware interrupt context, they all get rescheduled into a softirq for the real SKB freeing work anyways. So by doing it in NAPI poll, you're avoiding some needless overhead. BTW, it's insanely confusing that there is a function called qlge_msix_tx_isr() that of all things does RX work :-/ > 2) Change RSS queue count to match MSIx vector count instead > of CPU count. Some platforms didn't offer enough vectors > for our previous approach. Ideally you want "max(num_msix_vectors, num_cpus)" because if you hook up more MSIX vectors than you have cpus it's just extra overhead and depending upon the descrepency between the two counts it might unevenly distribute traffic work amongst the cpus. > 3) Change large RX buffer logic to use either multiple pages > or chunks of pages based on MTU and system page size. > > Examples: > > 64k Pages with 1500 MTU. The RX buffers size would be > 2048 bytes and there would be 32 per page. > > 4k pages with 9000 MTU. The RX buffer size would be 16k, > or 4 pages per buffer. This is wasteful, does the card have a mechnism by which it can dynamically carve up pages depending upon the actual frame size? If anything, make sure that skb->truesize gets set to something reasonable, or else TCP is going to reallocate SKBs when the receive queue limits are hit. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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