Date: Wed, 9 Dec 2015 23:03:19 -0500
From: Steven Rostedt <rostedt@goodmis.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: yalin wang <yalin.wang2010@gmail.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        "open list:MEMORY MANAGEMENT" <linux-mm@kvack.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>, Minchan Kim <minchan@kernel.org>,
        Sasha Levin <sasha.levin@oracle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Mel Gorman <mgorman@suse.de>, Michal Hocko <mhocko@suse.cz>
Subject: Re: [PATCH 1/2] mm, printk: introduce new format string for flags
Message-ID: <20151210040319.GB7814@home.goodmis.org>
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On Fri, Dec 04, 2015 at 03:15:45PM +0100, Vlastimil Babka wrote:
> On 12/03/2015 07:38 PM, yalin wang wrote:
> >that’s all, see cpumask_pr_args(masks) macro,
> >it also use macro and  %*pb  to print cpu mask .
> >i think this method is not very complex to use .
> 
> Well, one also has to write the appropriate translation tables.
> 
> >search source code ,
> >there is lots of printk to print flag into hex number :
> >$ grep -n  -r 'printk.*flag.*%x’  .
> >it will be great if this flag string print is generic.
> 
> I think it can always be done later, this is an internal API. For now we
> just have 3 quite generic flags, so let's not over-engineer things right
> now.
> 

As long as it is never used in the TP_printk() part of a tracepoint. As soon
as it is, trace-cmd and perf will update parse-events to handle that
parameter, and as soon as that is done, it becomes a userspace ABI.

Just be warned.

-- Steve

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