<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman","serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:#0563C1;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:#954F72;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-reply;
font-family:"Calibri","sans-serif";
color:#44546A;
font-weight:normal;
font-style:normal;
text-decoration:none none;}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri","sans-serif";}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="EN-US" link="#0563C1" vlink="#954F72">
<div class="WordSection1">
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri","sans-serif";color:#44546A">Hi Wenqian,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri","sans-serif";color:#44546A"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri","sans-serif";color:#44546A">Thank you for your inquiry. In the FindAdapter routine (in nvmeStd.c), the driver checks CAP.MQES and saves the value in pAE->InitInfo.IoQEntries (if the default
or register override is smaller than CAP.MQES, it is saved instead). Within the function NVMeAllocIoQueues, there is loop that will iterate to create queue pairs based on the number of cpu cores.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri","sans-serif";color:#44546A"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri","sans-serif";color:#44546A">In this loop, a call to NVMeAllocQueues is made. Just prior to this call, the value saved in pAE->InitInfo.IoQEntires is retrieved (stack variable “QEntres”)
and passed in as the 3<sup>rd</sup> parameter. So, once the allocation is taking place where you mention below, the 3<sup>rd</sup> parameter of the function has already been checked against CAP.MQES. Also, per the NVMe spec sections 5.3 and 5.4 – Figures 33
and 37 (create completion queue and submission queue PRP 1), all queue memory must be “physically contiguous and memory page aligned”.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri","sans-serif";color:#44546A"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri","sans-serif";color:#44546A">Thanks<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri","sans-serif";color:#44546A">Ray<o:p></o:p></span></p>
<p class="MsoNormal"><a name="_MailEndCompose"><span style="font-size:10.0pt;font-family:"Calibri","sans-serif";color:#44546A"><o:p> </o:p></span></a></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> nvmewin-bounces@lists.openfabrics.org [mailto:nvmewin-bounces@lists.openfabrics.org]
<b>On Behalf Of </b>Wenqian Wu<br>
<b>Sent:</b> Wednesday, February 11, 2015 4:58 PM<br>
<b>To:</b> nvmewin@lists.openfabrics.org<br>
<b>Subject:</b> [nvmewin] NVMe Queue entry number<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal">Hi OFA driver member,<o:p></o:p></p>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">I have one question regarding the Queue entry size. The driver will allocate number of entries aligned to memory page (line877, nvmeInit.c), instead of the actual queue size controller supports (CAP.MQES). Controller can return error if
host request more entries while ignoring controller's capability. I think as long as the base address is page aligned, there is no reason to make the entries number aligned to page boundary. Can this be considered a driver bug or is there any particular consideration? <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">Thanks,<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Wenqian <o:p></o:p></p>
</div>
</div>
</div>
</body>
</html>