On Tue, Nov 19, 2013 at 11:47:11AM +0900, Masatake YAMATO wrote: > I'm working on adding stack trace feature to strace(strace-k). In > addition to the name of invoked system call, strace-k prints the stack > trace of the process. > > libunwind is main part of the feature. After some testing I found > `_UPT_get_proc_name' is a performance bottleneck of the fuature. On > linux the function opens and scans /proc/$pid/maps(MAP) for each name > resolving. Generally MAP should be reread for each name resolution > because memory mapping of a process can be altered. However, strace > knows well when the memory mapping of the target process is altered > because strace tracks the invocations of system calls which modify > memory mapping. Therefore rereading is just inefficient for strace. I do not see any os-depended features ised in the map cache implementation you provide, am I mistaken ? If not, I do not understand why this should be linux-specific.
What I noted is that your cache uses malloc(). Note that both Linux and FreeBSD get_elf_image() avoid non-reentrant calls to allow the backtracing to work from signal handler context, in particular, the memory is allocated by direct mmap(2) use.
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