In the course of evaluating realtime kernels for an Intel Atom based setup, I ran across major read-speed problems on CIFS mounts when using a 3.12 kernel (also tried 3.10, same issue). This resulted in transmissions @ <800KB/s compared to >10MB when using 3.4 kernel's CIFS. At first I thought it had to do with either one of these old buffer size related solutions: https://bugzilla.samba.org/show_bug.cgi?id=7699 https://bugs.launchpad.net/ubuntu/+source/cifs-utils/+bug/810606 http://ubuntuforums.org/showthread.php?t=1578068 However, fiddling around with rsize/wsize, resp. CIFSMaxBufSize, did not change anything. Increasing the CIFS debug verbosity and dumping TCP traffic showed that in the 3.12 case, smaller packets are negotiated and transmitted which obviously results in lower throughput. Here are my test logs: Kernel 3.12.10-rt15 CIFS test log (slow speed): http://7f42b4439bec450b.paste.se Kernel 3.4.82-rt100 CIFS test log (normal speed): http://863be082c9262448.paste.se I'm all out of handles to crank, so before I dive further into the kernel's CIFS code, I thought I'd call out for some expert help to check if this is a known issue. Thanks in advance, Rolf Anderegg -- To unsubscribe from this list: send the line "unsubscribe linux-cifs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
