linux-kernel - Re: [PATCH 4/7] mm, vmscan: show LRU name in mm_vmscan_lru

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Date:   Tue, 3 Jan 2017 22:40:23 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>,
        Johannes Weiner <hannes@...xchg.org>,
        Rik van Riel <riel@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/7] mm, vmscan: show LRU name in mm_vmscan_lru_isolate
 tracepoint

On 01/03/2017 10:24 PM, Michal Hocko wrote:
> On Tue 03-01-17 21:52:44, Michal Hocko wrote:
>> On Tue 03-01-17 21:47:45, Michal Hocko wrote:
>> > On Tue 03-01-17 18:08:58, Vlastimil Babka wrote:
>> > > On 12/28/2016 04:30 PM, Michal Hocko wrote:
>> > > > From: Michal Hocko <mhocko@...e.com>
>> > > >
>> > > > mm_vmscan_lru_isolate currently prints only whether the LRU we isolate
>> > > > from is file or anonymous but we do not know which LRU this is. It is
>> > > > useful to know whether the list is file or anonymous as well. Change
>> > > > the tracepoint to show symbolic names of the lru rather.
>> > > >
>> > > > Signed-off-by: Michal Hocko <mhocko@...e.com>
>> > > > ---
>> > > >  include/trace/events/vmscan.h | 20 ++++++++++++++------
>> > > >  mm/vmscan.c                   |  2 +-
>> > > >  2 files changed, 15 insertions(+), 7 deletions(-)
>> > > >
>> > > > diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
>> > > > index 6af4dae46db2..cc0b4c456c78 100644
>> > > > --- a/include/trace/events/vmscan.h
>> > > > +++ b/include/trace/events/vmscan.h
>> > > > @@ -36,6 +36,14 @@
>> > > >  		(RECLAIM_WB_ASYNC) \
>> > > >  	)
>> > > >
>> > > > +#define show_lru_name(lru) \
>> > > > +	__print_symbolic(lru, \
>> > > > +			{LRU_INACTIVE_ANON, "LRU_INACTIVE_ANON"}, \
>> > > > +			{LRU_ACTIVE_ANON, "LRU_ACTIVE_ANON"}, \
>> > > > +			{LRU_INACTIVE_FILE, "LRU_INACTIVE_FILE"}, \
>> > > > +			{LRU_ACTIVE_FILE, "LRU_ACTIVE_FILE"}, \
>> > > > +			{LRU_UNEVICTABLE, "LRU_UNEVICTABLE"})
>> > > > +
>> > >
>> > > Does this work with external tools such as trace-cmd, i.e. does it export
>> > > the correct format file?
>> >
>> > How do I find out?

You did :) Another way to verify is to use trace-cmd tool instead of manual 
sysfs operations and see if the output looks as expected. The tool gets the raw 
records from kernel and does the printing in userspace, unlike "cat trace_pipe".

>> Well, I've just checked the format file and it says
>> print fmt: "isolate_mode=%d classzone=%d order=%d nr_requested=%lu nr_scanned=%lu nr_skipped=%lu nr_taken=%lu lru=%s", REC->isolate_mode, REC->classzone_idx, REC->order, REC->nr_requested, REC->nr_scanned, REC->nr_skipped, REC->nr_taken, __print_symbolic(REC->lru, {LRU_INACTIVE_ANON, "LRU_INACTIVE_ANON"}, {LRU_ACTIVE_ANON, "LRU_ACTIVE_ANON"}, {LRU_INACTIVE_FILE, "LRU_INACTIVE_FILE"}, {LRU_ACTIVE_FILE, "LRU_ACTIVE_FILE"}, {LRU_UNEVICTABLE, "LRU_UNEVICTABLE"})
>>
>> So the tool should be OK as long as it can find values for LRU_*
>> constants. Is this what is the problem?

Exactly.

> OK, I got it. We need enum->value translation and all the EM stuff to do
> that, right?

Yep.

> I will rework the patch and move the definition to the rest of the EM
> family...

Thanks!