Em Mon, Apr 25, 2016 at 01:06:48PM -0700, Alexei Starovoitov escreveu: > On Mon, Apr 25, 2016 at 04:22:29PM -0300, Arnaldo Carvalho de Melo wrote: > > Em Mon, Apr 25, 2016 at 01:27:06PM -0300, Arnaldo Carvalho de Melo escreveu: > > > Em Mon, Apr 25, 2016 at 01:14:25PM -0300, Arnaldo Carvalho de Melo > > > escreveu: > > > > Em Fri, Apr 22, 2016 at 03:18:08PM -0700, Alexei Starovoitov escreveu: > > > > > right... and looking into it further, realized that the patch is > > > > > broken, > > > > > since get_callchain_entry() is doing: > > > > > return &entries->cpu_entries[cpu][*rctx]; > > > > > whereas it should be dynamic offset based on > > > > > sysctl_perf_event_max_stack*8 > > > > > So definitely needs another respin. > > > > > struct perf_callchain_entry { > > > __u64 nr; > > > __u64 ip[0]; /* /proc/sys/kernel/perf_event_max_stack */ > > > }; > > > > > But perf_callchain_entry->ip is not a pointer... Got it ;-\ > > > > This is what I am building now, a patch on top of the previous, that > > will be combined and sent as v3, if I don't find any more funnies: > > > > diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c > > index 6fe77349fa9d..40657892a7e0 100644 > > --- a/kernel/events/callchain.c > > +++ b/kernel/events/callchain.c > > @@ -20,11 +20,10 @@ struct callchain_cpus_entries { > > > > int sysctl_perf_event_max_stack __read_mostly = PERF_MAX_STACK_DEPTH; > > > > -static size_t perf_callchain_entry__sizeof(void) > > -{ > > - return sizeof(struct perf_callchain_entry) + > > - sizeof(__u64) * sysctl_perf_event_max_stack; > > -} > > +#define __perf_callchain_entry_size(entries) \ > > + (sizeof(struct perf_callchain_entry) + sizeof(__u64) * entries) > > + > > +static size_t perf_callchain_entry_size __read_mostly = > > __perf_callchain_entry_size(PERF_MAX_STACK_DEPTH); > > > > static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]); > > static atomic_t nr_callchain_events; > > @@ -81,7 +80,7 @@ static int alloc_callchain_buffers(void) > > if (!entries) > > return -ENOMEM; > > > > - size = perf_callchain_entry__sizeof() * PERF_NR_CONTEXTS; > > + size = perf_callchain_entry_size * PERF_NR_CONTEXTS; > > > > for_each_possible_cpu(cpu) { > > entries->cpu_entries[cpu] = kmalloc_node(size, GFP_KERNEL, > > @@ -155,7 +154,8 @@ static struct perf_callchain_entry > > *get_callchain_entry(int *rctx) > > > > cpu = smp_processor_id(); > > > > - return &entries->cpu_entries[cpu][*rctx]; > > + return (((void *)&entries->cpu_entries[cpu][0]) + > > + (*rctx * perf_callchain_entry_size)); > > I think the following would be easier to read: > > + return (void *)entries->cpu_entries[cpu] + > + *rctx * perf_callchain_entry_size;
Well, I thought that multiline expressions required parentheses, to make them easier to read for someone, maybe Ingo? ;-) Whatever, both generate the same result, really want me to change this? > ? > if didn't mixed up the ordering... If you are not sure, then its not clearer, huh? ;-P > and probably we could do the math on the spot instead of introducing > perf_callchain_entry_size global variable? I was trying to avoid the calc for each alloc, just doing it when we change that number via the sysctl, probably not that big a deal, do you really think we should do the math per-alloc instead of per-sysctl-changing? - Arnaldo