Messages in this thread | | | Date | Wed, 6 May 2015 15:13:15 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH V7 3/6] perf, x86: handle multiple records in PEBS buffer |
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On Wed, May 06, 2015 at 03:01:16PM +0200, Andi Kleen wrote: > > > > + if (p->status != (1 << bit)) { > > > > + u64 pebs_status; > > > > + > > > > + /* slow path */ > > > > + pebs_status = p->status & cpuc->pebs_enabled; > > > > + pebs_status &= (1ULL << MAX_PEBS_EVENTS) - 1; > > > > + if (pebs_status != (1 << bit)) { > > > > + perf_log_lost(event); > > > > > > Does it make sense to keep an error[bit] count and only log once with the > > > actual number in? -- when !0 obviously. > > > > Yes, will do it. > > If you use anything but u8 for the array member it would be too large > for the NMI stack, and u8 is lilkely overflow prone. Would not do it.
If we're so close that 4*8=32 bytes would overflow the stack we're in trouble already.
But we could just switch counts[] over to short and have another short array for errors[], that way no extra bytes of stack used.
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