On Mon, Mar 2, 2015 at 8:46 AM, Tom Zanussi <tom.zanu...@linux.intel.com> wrote: > On Mon, 2015-03-02 at 11:37 -0500, Steven Rostedt wrote: >> On Mon, 2 Mar 2015 10:01:00 -0600 >> Tom Zanussi <tom.zanu...@linux.intel.com> wrote: >> >> > Add a gfp flag that allows kmalloc() et al to be used in tracing >> > functions. >> > >> > The problem with using kmalloc for tracing is that the tracing >> > subsystem should be able to trace kmalloc itself, which it can't do >> > directly because of paths like kmalloc()->trace_kmalloc()->kmalloc() >> > or kmalloc()->trace_mm_page_alloc()->kmalloc(). >> >> This part I don't like at all. Why can't the memory be preallocated >> when the hist is created (the echo 'hist:...')? >> > > Yeah, I didn't like it either. My original version did exactly what you > suggest and preallocated an array of entries to 'allocate' from in order > to avoid the problem. > > But I wanted to attempt to use the bpf_map directly, which already uses > kmalloc internally. My fallback in case this wouldn't fly, which it > obviously won't, would be to add an option to have the bpf_map code > preallocate a maximum number of entries or pass in a client-owned array > for the purpose. I'll do that if I don't hear any better ideas..
Tom, I'm still reading through the patch set. Quick comment for the above. Currently there are two map types: array and hash. array type is pre-allocating all memory at map creation time. hash is allocating on demand. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/