On Sat, Aug 10, 2013 at 9:26 AM, zhangwei(Jovi) <jovi.zhang...@gmail.com> wrote: > On Sat, Aug 10, 2013 at 12:20 AM, Oleg Nesterov <o...@redhat.com> wrote: >> >> Sorry, I didn't read this series yet. Not that I think this needs my >> help, but I'll try to do this a later... >> >> On 08/09, Masami Hiramatsu wrote: >> > >> > I just concern using kmalloc() in the event handler. >> >> GFP_KERNEL should be fine for uprobe handler. >> >> However, iirc this conflicts with the patches from Jovi, >> "Support ftrace_event_file base multibuffer" adds rcu_read_lock() >> around uprobe_trace_print(). > > (Sorry about html text rejected by kernel.org, send again with plain text.) > > Then we might need to call kmalloc before rcu_read_lock, also call kfree > after rcu_read_unlock. > > And it's not needed to call kmalloc for each instances in multi-buffer > case, just > kmalloc once is enough. > > I also have same concern about use kmalloc in uprobe handler, use kmalloc > in uprobe handler seems have a little overhead, why not pre-allocate one page > static memory for temp buffer(perhaps trace_uprobe based)? one page size > would be enough for all uprobe args storage, then we don't need to call > kmalloc in that "fast path". > forgotten to say, that pre-allocated buffer would need to be per-cpu, to prevent buffer corruption.
It's a memory space vs. performance trade-off problem. :) > > Thanks. >> >> >> Steven, Jovi, what should we do with that patch? It seems that it >> was forgotten. >> >> I can take these patches into my ubprobes branch and then ask Ingo >> to pull. But this will complicate the routing of the new changes >> like this. >> >> Oleg. -- 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/
