> I thought that an mmiowb() was called for here (to order the PIO > writes above more cheaply than doing the readq()). I posted a > patch like this some time ago: > > http://marc.theaimsgroup.com/?l=linux-netdev&m=111508292028110&w=2
On an Altix machine I believe the readq was necessary to flush the PIO writes. How long did you run the tests? I had seen in long duration tests that an occasional write (TXDL control word and the address) would be missed and the xmit Get's stuck. > > FWIW, I've done quite a few performance measurements with the patch > I posted earlier, and it's worked well. For 1500 byte mtus throughput > goes up by ~20%. Is even the mmiowb() unnecessary? > Was this on 2.4 kernel because I think the readq would not have a significant impact on 2.6 kernels due to TSO. (with TSO on the number of packets that actually enter the Xmit routine would be reduced apprx 40 times). > What is the wmb() above for? wmb() is to ensure ordered PIO writes. Thanks - Koushik > -----Original Message----- > From: Arthur Kepner [mailto:[EMAIL PROTECTED] > Sent: Thursday, July 07, 2005 4:15 PM > To: [EMAIL PROTECTED] > Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED]; > netdev@vger.kernel.org; [EMAIL PROTECTED]; > [EMAIL PROTECTED]; [EMAIL PROTECTED] > Subject: Re: [PATCH 2.6.12.1 5/12] S2io: Performance improvements > > > On Thu, 7 Jul 2005 [EMAIL PROTECTED] wrote: > > > ....... > > 2. Removed unnecessary PIOs(read/write of tx_traffic_int and > > rx_traffic_int) from interrupt handler and removed read of > > general_int_status register from xmit routine. > > > ...... > > @@ -2891,6 +2869,8 @@ int s2io_xmit(struct sk_buff *skb, struc > > val64 = > mac_control->fifos[queue].list_info[put_off].list_phy_addr; > > writeq(val64, &tx_fifo->TxDL_Pointer); > > > > + wmb(); > > + > > val64 = (TX_FIFO_LAST_TXD_NUM(frg_cnt) | TX_FIFO_FIRST_LIST | > > TX_FIFO_LAST_LIST); > > > > @@ -2900,9 +2880,6 @@ int s2io_xmit(struct sk_buff *skb, struc > > #endif > > writeq(val64, &tx_fifo->List_Control); > > > > - /* Perform a PCI read to flush previous writes */ > > - val64 = readq(&bar0->general_int_status); > > - > > put_off++; > > I thought that an mmiowb() was called for here (to order the PIO > writes above more cheaply than doing the readq()). I posted a > patch like this some time ago: > > http://marc.theaimsgroup.com/?l=linux-netdev&m=111508292028110&w=2 > > FWIW, I've done quite a few performance measurements with the patch > I posted earlier, and it's worked well. For 1500 byte mtus throughput > goes up by ~20%. Is even the mmiowb() unnecessary? > > What is the wmb() above for? > > -- > Arthur > - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
