On Sat, 17 Nov 2007 21:31:25 -0800 "kernel coder" <[EMAIL PROTECTED]> wrote:
> hi, > I'm trying to add some code to netif_receive_skb function in > dev.c file . The cycles consumed by that code was around 16 cycles on > Dual Core Opetron machine.I'm working on that code for last 6 months > now and the consumed cycles have always been around 16 cycles .I don't > touch any other part of kernel . > > But for last 4 days the consumed cycles have suddenly increased to > around 35 cycles . I'm using RDTSC instruction to profile the > code.There is no change in code and the kernel version is also the > same .I am assuming that there must be something wrong with hardware. note that profiling a section that takes this short with rdtsc is... not really working well in practice; you're profiling something that's smaller (or at least roughly the same size) than the cpu's out of order speculation window, so your rdtsc greatly impacts what is actually happening in the code. as for the change... 16->35 cycles can well be a code or data alignment change or even a branch misprediction due to some minor code generation issue.... you're looking at a small microscopic part of the universe after all, the butterfly in the pacific WILL influence you ;-) -- If you want to reach me at my work email, use [EMAIL PROTECTED] For development, discussion and tips for power savings, visit http://www.lesswatts.org - 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/
