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Message-ID: <47093C7A.1030203@garzik.org> Date: Sun, 07 Oct 2007 16:07:22 -0400 From: Jeff Garzik <jeff@...zik.org> To: Yinghai Lu <yhlu.kernel@...il.com> CC: netdev@...r.kernel.org, Ayaz Abdulla <aabdulla@...dia.com>, LKML <linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [PATCH 2/5] forcedeth: interrupt handling cleanup Yinghai Lu wrote: > On 10/7/07, Jeff Garzik <jeff@...zik.org> wrote: >> Yinghai Lu wrote: >>> On 10/6/07, Jeff Garzik <jeff@...zik.org> wrote: >>>> commit a606d2a111cdf948da5d69eb1de5526c5c2dafef >>>> Author: Jeff Garzik <jeff@...zik.org> >>>> Date: Fri Oct 5 22:56:05 2007 -0400 >>>> >>>> [netdrvr] forcedeth: interrupt handling cleanup >>>> >>>> * nv_nic_irq_optimized() and nv_nic_irq_other() were complete duplicates >>>> of nv_nic_irq(), with the exception of one function call. Consolidate >>>> all three into a single interrupt handler, deleting a lot of redundant >>>> code. >>>> >>>> * greatly simplify irq handler locking. >>>> >>>> Prior to this change, the irq handler(s) would acquire and release >>>> np->lock for each action (RX, TX, other events). >>>> >>>> For the common case -- RX or TX work -- the lock is always acquired, >>>> making all successive acquire/release combinations largely redundant. >>>> >>>> Acquire the lock at the beginning of the irq handler, and release it at >>>> the end of the irq handler. This is simple, easy, and obvious. >>>> >>>> * remove irq handler work loop. >>>> >>>> All interesting events emanating from the irq handler either have >>>> their own work loops, or they poke a timer into action. >>>> >>>> Therefore, delete the pointless master interrupt handler work loop. >>>> >>>> Signed-off-by: Jeff Garzik <jgarzik@...hat.com> >>>> >> Do you have ideas/suggestions for a different method? > > in the e1000 driver, it has seperate handler for msi and ioapic. > > but in forcedeth, the nv_nic_irq_optimized keep check msi_flags..., > with num of msi interrupt number, that could cause cpu loading get a > little bit high..., even the network performance is ok. With all the activity in the interrupt handler, a few in-cache branches are definitely going to be lost in the noise. Separating the interrupt handlers between MSI and non-MSI tends to be of more benefit when the separation is accompanied by more efficient locking in the MSI interrupt handler, or a different mode of interrupt clear, or some other attribute. Though CPU usage would be a good thing to measure, with these patches. Jeff - 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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