linux-kernel - Re: [PATCH 2/2] mm: compaction.c: Add/Modify direct compaction tracepoints

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Date:	Sun, 7 Aug 2016 18:02:41 +0530
From:	Janani Ravichandran <janani.rvchndrn@...il.com>
To:	Vlastimil Babka <vbabka@...e.cz>
Cc:	Janani Ravichandran <janani.rvchndrn@...il.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, riel@...riel.com,
	akpm@...ux-foundation.org, hannes@...pxchg.org,
	vdavydov@...tuozzo.com, mhocko@...e.com,
	mgorman@...hsingularity.net, kirill.shutemov@...ux.intel.com,
	bywxiaobai@....com, rostedt@...dmis.org
Subject: Re: [PATCH 2/2] mm: compaction.c: Add/Modify direct compaction tracepoints


> On Aug 1, 2016, at 6:55 PM, Vlastimil Babka <vbabka@...e.cz> wrote:
> 
> 
> Yea, this tracepoint has been odd in not printing node/zone in a friendly way (it's possible to determine it from zone_start/zone_end though, so this is good in general. But instead of printing nid and zid like this, it would be nice to unify the output with the other tracepoints, e.g.:
> 
> DECLARE_EVENT_CLASS(mm_compaction_suitable_template,
> [...]
>        TP_printk("node=%d zone=%-8s order=%d ret=%s",
>                __entry->nid,
>                __print_symbolic(__entry->idx, ZONE_TYPE),

Sure, I’ll do that in v2. Thanks!

Also, I guess I should have mentioned that the tracepoint added
at the end of the compaction code wasn’t just for deriving latency information. 
rc and *contended would give us the result of the compaction attempted, 
which I thought would be useful.

I get that begin/end tracepoints aren’t required here, but how about having
trace_mm_compaction_try_to_compact_pages moved to the end to 
include compaction status?

Janani.
> 
> Thanks,
> Vlastimil