Hi folks, I'm trying to work out the source of some pretty poor read performance I'm seeing over iSCSI. I'm doing all my testing using a 16GB rd_mcp backstore over "crossover" 10G ethernet between my target and initiator with no switches in between. I'm seeing 780MB/sec sequential writes (testing with dd) but "only" 520-550MB/sec reads. The target is a fairly beefy dual Xeon E5 machine, while the initiator is an older Xeon 5148. Both are using Solarflare SFN5162F 10G ethernet cards with kernel 3.14.5 (from Debian). I can easily saturate the link using iperf, although admittedly CPU usage is high when doing so. I'm running irqbalance on both ends and MTU is 9000. This is a fairly typical run: # dd if=/dev/zero of=/dev/sdg bs=1M dd: writing `/dev/sdg': No space left on device 16385+0 records in 16384+0 records out 17179869184 bytes (17 GB) copied, 21.3697 s, 804 MB/s # dd if=/dev/sdg of=/dev/null bs=1M 16384+0 records in 16384+0 records out 17179869184 bytes (17 GB) copied, 31.2977 s, 549 MB/s Most of the system setting on both sides are fairly vanilla as the things I've tried so far haven't had very much effect. The only real changes I have now are: net.core.rmem_max = 16777216 net.core.wmem_max = 16777216 It feels like there's a bottleneck somewhere but I can't quite put my finger on it. All suggestions gratefully received. Best regards, Chris -- Chris Boot Tiger Computing Ltd "Linux for Business" Tel: 01600 483 484 Web: http://www.tiger-computing.co.uk Follow us on Facebook: http://www.facebook.com/TigerComputing Registered in England. Company number: 3389961 Registered address: Wyastone Business Park, Wyastone Leys, Monmouth, NP25 3SR -- To unsubscribe from this list: send the line "unsubscribe target-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
