On Mon, 8 May 2023 11:57:10 -0400 Kent Overstreet <kent.overstreet@xxxxxxxxx> wrote: > On Mon, May 08, 2023 at 05:52:06PM +0200, Petr Tesařík wrote: > > On Sun, 7 May 2023 13:20:55 -0400 > > Kent Overstreet <kent.overstreet@xxxxxxxxx> wrote: > > > > > On Thu, May 04, 2023 at 11:07:22AM +0200, Michal Hocko wrote: > > > > No. I am mostly concerned about the _maintenance_ overhead. For the > > > > bare tracking (without profiling and thus stack traces) only those > > > > allocations that are directly inlined into the consumer are really > > > > of any use. That increases the code impact of the tracing because any > > > > relevant allocation location has to go through the micro surgery. > > > > > > > > e.g. is it really interesting to know that there is a likely memory > > > > leak in seq_file proper doing and allocation? No as it is the specific > > > > implementation using seq_file that is leaking most likely. There are > > > > other examples like that See? > > > > > > So this is a rather strange usage of "maintenance overhead" :) > > > > > > But it's something we thought of. If we had to plumb around a _RET_IP_ > > > parameter, or a codetag pointer, it would be a hassle annotating the > > > correct callsite. > > > > > > Instead, alloc_hooks() wraps a memory allocation function and stashes a > > > pointer to a codetag in task_struct for use by the core slub/buddy > > > allocator code. > > > > > > That means that in your example, to move tracking to a given seq_file > > > function, we just: > > > - hook the seq_file function with alloc_hooks > > > > Thank you. That's exactly what I was trying to point out. So you hook > > seq_buf_alloc(), just to find out it's called from traverse(), which > > is not very helpful either. So, you hook traverse(), which sounds quite > > generic. Yes, you're lucky, because it is a static function, and the > > identifier is not actually used anywhere else (right now), but each > > time you want to hook something, you must make sure it does not > > conflict with any other identifier in the kernel... > > Cscope makes quick and easy work of this kind of stuff. Sure, although AFAIK the index does not cover all possible config options (so non-x86 arch code is often forgotten). However, that's the less important part. What do you do if you need to hook something that does conflict with an existing identifier? Petr T
