cc'ing netdev Robert Hancock wrote: > Srivatsa Vaddagiri wrote: >> Hi, >> I happened to look at a system which was exhibiting poor ping >> performance with e1000 driver (in 2.6.25) and had some questions >> regarding that. >> >> Ping test was done between the system and a laptop, which were connected >> using a straight ethernet cable. Ping reported round trip times running >> into seconds (!) and also packet loss. >> >> Upon some investigation, I found that the interrupt count field in >> /proc/interrupts (associated with eth1) is not incrementing as fast as >> it should. Moreover eth1 interrupt line is shared with the hard disk >> interrupt (ata_piix) as below: >> >> # cat /proc/interrupts >> >> . >> >> 10: 2296 XT-PIC-XT ata_piix, eth0, eth1 >> >> . >> >> IRQ10 is thus being shared by both the hard disk and eth0/eth1. >> >> Here's the strange observation I made: >> >> When I initiate some disk activity (ex: dd if=/dev/zero >> of=/tmp/file), ping performance suddently shot up (round trip time in >> double digits ms, 0% packet loss)! I presume this is because that >> e1000 intr handler is called >> whenever there was a interrupt from hard disk on IRQ10, which polled >> NIC and processed packets immediately. >> >> As soon as I kill the background disk-write intensive job, ping >> performance again dropped. >> >> This meant that e1000 NIC is having trouble interrupting the OS. >> >> Before I could jump up and say this is a hardware issue, I was told >> that Windows works just fine on the server (and as well as 2.4 kernel, >> which I couldnt verify) :( >> >> >> Some more observations: >> >> 1. I tried setting e1000 parameters (RxIntDelay=0, RxAbsIntDelay=0, >> TxIntDelay=0, TxAbsIntDelay=0, InterruptThrottleRate=0). None of >> them helped. >> >> 2. When ping performance was poor, readprofile showed that system >> is mostly idle. This confirms that OS is not getting very >> frequenty interrupts from eth1 and hence idling. >> >> 3. When ping performance was poor, ethtool -S eth1 showed that >> rx_bytes was incrementing at a good pace, showing that the NIC >> was receiving ping responses back, but not handing them over >> to OS for further processing >> >> 4. e1000 chipset is 82546GB >> >> 5. e1000e driver didnt work at all (it doesnt recognize the cards). >> >> >> Any advice on how to fix this problem? > > Can you post your dmesg output from bootup with no special options > (noacpi, etc.) enabled? > -- > To unsubscribe from this list: send the line "unsubscribe > linux-kernel" in > the body of a message to [EMAIL PROTECTED] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
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