Messages in this thread Patch in this message | | | From | Jacek Tomaka <> | Date | Tue, 31 Jul 2018 00:29:25 +0800 | Subject | Re: [PATCH v2] perf/x86/intel: Add support for MISPREDICT bit on Knights Landing cpus |
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<div dir="ltr">I do not understand the difference between linear address vs effective address but LBR_FORMAT_EIP_FLAGS implies effective address, no?<div><div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jul 31, 2018 at 12:17 AM, Peter Zijlstra <span dir="ltr"><<a href="mailto:peterz@infradead.org" target="_blank">peterz@infradead.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="HOEnZb"><div class="h5">On Mon, Jul 30, 2018 at 10:28:13PM +0800, Jacek Tomaka wrote:<br> > From: Jacek Tomaka <<a href="mailto:jacek.tomaka@poczta.fm">jacek.tomaka@poczta.fm</a>><br> > <br> > Problem: perf did not show branch predicted/mispredicted bit in brstack.<br> > <br> > Output of perf -F brstack for profile collected<br> > <br> > Before: <br> > 0x4fdbcd/0x4fdc03/-/-/-/0<br> > 0x45f4c1/0x4fdba0/-/-/-/0<br> > 0x45f544/0x45f4bb/-/-/-/0<br> > 0x45f555/0x45f53c/-/-/-/0<br> > 0x7f66901cc24b/0x45f555/-/-/-/<wbr>0<br> > 0x7f66901cc22e/0x7f66901cc23d/<wbr>-/-/-/0<br> > 0x7f66901cc1ff/0x7f66901cc20f/<wbr>-/-/-/0<br> > 0x7f66901cc1e8/0x7f66901cc1fc/<wbr>-/-/-/0<br> > <br> > After: <br> > 0x4fdbcd/0x4fdc03/P/-/-/0<br> > 0x45f4c1/0x4fdba0/P/-/-/0<br> > 0x45f544/0x45f4bb/P/-/-/0<br> > 0x45f555/0x45f53c/P/-/-/0<br> > 0x7f66901cc24b/0x45f555/P/-/-/<wbr>0<br> > 0x7f66901cc22e/0x7f66901cc23d/<wbr>P/-/-/0 <br> > 0x7f66901cc1ff/0x7f66901cc20f/<wbr>P/-/-/0<br> > 0x7f66901cc1e8/0x7f66901cc1fc/<wbr>P/-/-/0<br> > <br> > Cause: <br> > As mentioned in Software Development Manual vol 3, 17.4.8.1,<br> > IA32_PERF_CAPABILITIES[5:0] indicates the format of the address that is<br> > stored in the LBR stack. Knights Landing reports 1 (LBR_FORMAT_LIP) as<br> > its format. Despite that, registers containing FROM address of the branch,<br> > do have MISPREDICT bit but because of the format indicated in<br> > IA32_PERF_CAPABILITIES[5:0], LBR did not read MISPREDICT bit.<br> > <br> > Solution: <br> > Teach LBR about above Knights Landing quirk and make it read MISPREDICT bit.<br> > ---<br> > arch/x86/events/intel/lbr.c | 6 +++++-<br> > 1 file changed, 5 insertions(+), 1 deletion(-)<br> > <br> > diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c<br> > index cf372b9055..043aa09f3a 100644<br> > --- a/arch/x86/events/intel/lbr.c<br> > +++ b/arch/x86/events/intel/lbr.c<br> > @@ -19,7 +19,7 @@ enum {<br> > LBR_FORMAT_MAX_KNOWN = LBR_FORMAT_TIME,<br> > };<br> > <br> > -static const enum {<br> > +static enum {<br> > LBR_EIP_FLAGS = 1,<br> > LBR_TSX = 2,<br> > } lbr_desc[LBR_FORMAT_MAX_KNOWN + 1] = {<br> > @@ -1230,4 +1230,8 @@ void intel_pmu_lbr_init_knl(void)<br> > <br> > x86_pmu.lbr_sel_mask = LBR_SEL_MASK;<br> > x86_pmu.lbr_sel_map = snb_lbr_sel_map;<br> > +<br> > + /* Knights Landing does have MISPREDICT bit */<br> > + if (x86_pmu.intel_cap.lbr_format == LBR_FORMAT_LIP)<br> > + lbr_desc[LBR_FORMAT_LIP] |= LBR_EIP_FLAGS;<br> > }<br> <br> </div></div>So why not set lbr_format to LBR_FORMAT_EIP_FLAGS ?<br> </blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><span><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><font color="#000000"><font face="arial,helvetica,sans-serif"><b>Jacek Tomaka</b></font></font><br><font color="#000000"><font face="arial,helvetica,sans-serif"><font size="2">Geophysical Software Developer</font></font></font><br></div><font color="#000000" face="arial,helvetica,sans-serif"> </font><div><span lang="EN-US"></span> <span lang="EN-US"><b><br><br></b></span></div><font color="#000000" face="arial,helvetica,sans-serif"> </font><img src="http://drive.google.com/uc?export=view&id=0B4X9ixpc-ZU_NHV0WnluaXp5ZkE"><br><br><span style="color:rgb(102,102,102)"><font size="2"><b>DownUnder GeoSolutions<br><br></b></font></span><div><span style="color:rgb(102,102,102)"></span><span style="color:rgb(102,102,102)">76 Kings Park Road<br></span></div><span style="color:rgb(102,102,102)">West Perth 6005 WA, Australia<br><i><b>tel </b></i><a href="tel:+61%208%209287%204143" value="+61892874143" target="_blank">+61 8 9287 4143</a><br><a href="mailto:jacekt@dug.com" target="_blank">jacekt@dug.com</a><br><b><a href="http://www.dug.com" target="_blank">www.dug.com</a></b></span></div></div></div></div></div></div></span></div></div></div></div></div></div> </div></div></div></div>
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