Re: [BUG] perf: sampling with precise=2 broken in 3.18

2014-12-16 Thread Stephane Eranian
On Tue, Dec 16, 2014 at 5:46 AM, Peter Zijlstra wrote: > On Mon, Dec 15, 2014 at 11:51:07PM -0500, Stephane Eranian wrote: >> Hi, >> >> I was running some perf mem test for an upcoming patch when >> I realize that precise=2 was broken on 3.18. It seems it never >> (or extremely rarely) correct the

Re: [BUG] perf: sampling with precise=2 broken in 3.18

2014-12-16 Thread Peter Zijlstra
On Mon, Dec 15, 2014 at 11:51:07PM -0500, Stephane Eranian wrote: > Hi, > > I was running some perf mem test for an upcoming patch when > I realize that precise=2 was broken on 3.18. It seems it never > (or extremely rarely) correct the off-by-one error, when until 3.18-rc4 > it was 100% on the sa

[BUG] perf: sampling with precise=2 broken in 3.18

2014-12-15 Thread Stephane Eranian
Hi, I was running some perf mem test for an upcoming patch when I realize that precise=2 was broken on 3.18. It seems it never (or extremely rarely) correct the off-by-one error, when until 3.18-rc4 it was 100% on the same program. So something was introduced that broke the asm walker in perf_even