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Date:      Fri, 01 May 2015 10:47:43 -0400
From:      John Baldwin <jhb@freebsd.org>
To:        Gleb Smirnoff <glebius@freebsd.org>
Cc:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   Re: svn commit: r282280 - in head/sys/dev: e1000 ixgbe ixl
Message-ID:  <2197979.EUYqekgM4M@ralph.baldwin.cx>
In-Reply-To: <20150501135134.GC546@FreeBSD.org>
References:  <201504301823.t3UINd74073186@svn.freebsd.org> <1998053.shmPH6saZj@ralph.baldwin.cx> <20150501135134.GC546@FreeBSD.org>

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On Friday, May 01, 2015 04:51:34 PM Gleb Smirnoff wrote:
> On Fri, May 01, 2015 at 09:11:54AM -0400, John Baldwin wrote:
> J> > On Thu, Apr 30, 2015 at 06:23:39PM +0000, John Baldwin wrote:
> J> > J> Author: jhb
> J> > J> Date: Thu Apr 30 18:23:38 2015
> J> > J> New Revision: 282280
> J> > J> URL: https://svnweb.freebsd.org/changeset/base/282280
> J> > J> 
> J> > J> Log:
> J> > J>   Various fixes to the stats in igb(4), ixgbe(4), and ixl(4).
> J> > J>   - Use hardware counters for ifnet stats in igb(4) when possible.  This
> J> > J>     ensures these stats include packets that bypass the regular stack via
> J> > J>     netmap.
> J> > J>   - Don't derefence values off the end of the igb(4) VF stats structure.
> J> > J>     Instead, add a dedicated if_get_counter method for igb(4) VF interfaces.
> J> > J>   - Report missed packets on igb(4) as input queue drops rather than an
> J> > J>     input error.
> J> > J>   - Report bug_ring drop counts as output queue drops for igb(4) and ixgbe(4).
> J> > J>   - Export the buf_ring drop stats for individual rings via sysctl on
> J> > J>     ixgbe(4).^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> J> >        ^^^^^^^^^
> J> > 
> J> > While you are here, let me remind you about this plan:
> J> > 
> J> > https://lists.freebsd.org/pipermail/svn-src-head/2014-October/063575.html
> J> > 
> J> > We can prototype the API to userland now, write down a utility that uses
> J> > it, or add the functionality to an existing utility. And start with Intel
> J> > drivers, that seem to be most interested in extra stats.
> J> 
> J> So the importaing thing here is that if_get_counter() is still doing
> J> per-ifnet stats.  The stat you underlined above is per-queue instead.
> J> We well need more explicitly knowledge of queues outside of drivers
> J> and in the stack itself to support a generic framework for per-queue
> J> stats.
> 
> This depends on how generic we want the API to be. Of course, we can add
> an extra argument to if_get_counter().
> 
> However, if we don't expect the number of queues to exceed a reasonable
> number of 255 :), we can fit the functionality into existing API.
> We can keep the queue number in the highest 8 bits of the ift_counter
> parameter.
> 
> #define	IFCOUNTER_MASK		0x00ffffff
> #define	IFCOUNTER_QUEUE(c)	((c) >> 24)

I'd prefer that expose queues more directly and figure out how to handle
per-queue stats then (e.g. do we have some sort of driver-independent
structure that each ifnet has 1 or more of that maps to a queue and has
driver provided methods, etc.  If so you could have a driver method for
queue stats).  Note that I did use if_get_counter to report the
per-interface stats instead of adding a new sysctl.

-- 
John Baldwin



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