Re: [PATCH 1/3] mm/compaction: enhance trace output to know more about compaction internals

[Mel Gorman <mgorman@suse.de>]

On Thu, Jan 08, 2015 at 09:46:27AM +0100, Vlastimil Babka wrote:
> On 01/08/2015 09:18 AM, Joonsoo Kim wrote:
> > On Tue, Jan 06, 2015 at 10:05:39AM +0100, Vlastimil Babka wrote:
> >> On 12/03/2014 08:52 AM, Joonsoo Kim wrote:
> >> > It'd be useful to know where the both scanner is start. And, it also be
> >> > useful to know current range where compaction work. It will help to find
> >> > odd behaviour or problem on compaction.
> >> 
> >> Overall it looks good, just two questions:
> >> 1) Why change the pfn output to hexadecimal with different printf layout and
> >> change the variable names and? Is it that better to warrant people having to
> >> potentially modify their scripts parsing the old output?
> > 
> > Deciaml output has really bad readability since we manage all pages by order
> > of 2 which is well represented by hexadecimal. With hex output, we can
> > easily notice whether we move out from one pageblock to another one.
> 
> OK. I don't have any strong objection, maybe Mel should comment on this as the
> author of most of the tracepoints? But if it happens, I think converting the old
> tracepoints to new hexadecimal format should be a separate patch from adding the
> new ones.
> 

To date, I'm not aware of any user-space programs that heavily depend on
the formatting. The scripts I am aware of are ad-hoc and easily modified
to adapt to format changes. LTT-NG is the only tool that might be
depending on trace point formats but I severely doubt it's interested in
this particular tracepoint.

-- 
Mel Gorman
SUSE Labs

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