hi :-) 2011/2/16 Mulyadi Santosa <mulyadi.santosa@xxxxxxxxx>: > Hi :) > > On Wed, Feb 16, 2011 at 12:59, Rajat Jain <rajatjain@xxxxxxxxxxx> wrote: >> Hello loody, >> >>> 1. in kernel/trace, I always see "__read_mostly" at the end of >>> parameter is that a compiler optimization parameter? >> >> Yes, it is a hint to the compiler that the parameter is mostly read, thus if the compiler has to make a decision between optimizing one of the read / write paths, it will optimize the read path even at the expense of write path. > > > To be precise, they will be grouped into same cache line as much as > possible. By doing so, those cache line won't be invalidated so often > (keeping them "hot" :) hehehhe ) I cannot find it on the gcc manual. is it a option in kernel for kernel usage? if so, where I can found them. If not, can I use it on normal user level program? BTW, i have some more questions (since it is also related to kernel, I append in the same mail) 1. the parameters we pass to ftrace_trace_function are (unsigned long ip, unsigned long parent_ip), which are previous and pre-previous return address. what can we do on these 2 addresses? 2. per kernel document, HAVE_FUNCTION_TRACE_MCOUNT_TEST is used for " an optional optimization for the normal case" and there is a pseudo sample code such as + if (function_trace_stop) + return; so the optimization the config did is judge whether "function_trace_stop" before operation, right? Meanwhile, I found this judgement seems enable in ftrace_test_stop_func and it is located at #ifndef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST. The source code seems quite conflict with the document. -- Appreciate your kind help, miloody _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
