On Tue, May 3, 2011 at 2:32 AM, Abu Rasheda <rcpilot2010@gmail.com> wrote:
I am testing my driver on much faster host processor and facing following issues:
My host is too powerful and it can fill up device buffer queue very fast.
I get best performance when I do busy wait, but this is not desirable and is bad design.
I need to sleep and wake up quickly and predictability. Indication from device that queue has space, is coming in form of memory write (device writes to a memory location of i86 processor).
I tried using wait_event_interruptible_timeout, I am depending on 2nd parameter of the function but it wake up is too slow, even tried using value of 1.
Any suggestions ?
Many of us are just newbies in this area, and therefore, get it working is much more important than to optimize it - u can safely said that the hardcore kernel developer has already optimize many of these problems away, and so if they cannot do it, there must be a reason...try to probe more first perhaps. High speed networking device has many special hardware features: IP/UDP/TCP checksum offload etc. http://www.fenrus.org/how-to-not-write-a-device-driver-paper.pdf http://www.sun.com/products/networking/infiniband/ibhcaPCI-E/docs/datasheet.... Read this about NAPI: http://www.linuxfoundation.org/collaborate/workgroups/networking/napi <http://www.linuxfoundation.org/collaborate/workgroups/networking/napi>Eg, "Interrupt mitigation" - whereby interrupt mechanism is disabled (in particular my desktop PC's r8196.c is using this feature) and polling takes over instead - but u have to implemented complicated mechanism to reinject the interrupt if necessary (read r8196.c). And if u really ready....this is a good writeup: http://datatag.web.cern.ch/datatag/howto/tcp.html Other possible suggestion/features: Jumbo frames: http://www.cyberciti.biz/faq/rhel-centos-debian-ubuntu-jumbo-frames-configur... PCI posting (pdf paper above and r8196.c). Disabling TCP software checksum (and use the hardware instead): http://www.linuxquestions.org/questions/linux-enterprise-47/how-to-disable-t... And for loads of other ideas (eg, TCP bypass): * http://ttthebear.blogspot.com/2008/07/linux-kernel-bypass-and-performance.ht... * Generally a lot of these ideas can be found in the kernel source codes - just search and copy the implementation.....the highest network data transfer is achieved in infiniband-based Mellanox card (in some China supercomputer), and this involved the use of GPU technology etc.... https://lists.sdsc.edu/pipermail/npaci-rocks-discussion/2009-May/039639.html -- Regards, Peter Teoh