linux-kernel - Re: [bug, 4.8] /proc/meminfo: counter values are very wrong

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Message-ID: <20160805115935.GI16044@dastard>
Date:	Fri, 5 Aug 2016 21:59:35 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Mel Gorman <mgorman@...hsingularity.net>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [bug, 4.8] /proc/meminfo: counter values are very wrong

On Fri, Aug 05, 2016 at 11:54:17AM +0100, Mel Gorman wrote:
> On Fri, Aug 05, 2016 at 09:11:10AM +1000, Dave Chinner wrote:
> > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > > index fb975cec3518..baa97da3687d 100644
> > > --- a/mm/page_alloc.c
> > > +++ b/mm/page_alloc.c
> > > @@ -4064,7 +4064,7 @@ long si_mem_available(void)
> > >  	int lru;
> > >  
> > >  	for (lru = LRU_BASE; lru < NR_LRU_LISTS; lru++)
> > > -		pages[lru] = global_page_state(NR_LRU_BASE + lru);
> > > +		pages[lru] = global_node_page_state(NR_LRU_BASE + lru);
> > >  
> > >  	for_each_zone(zone)
> > >  		wmark_low += zone->watermark[WMARK_LOW];
> > 
> > OK, that makes the /proc accounting match the /sys per-node
> > accounting, but the output still looks wrong. I remove files with
> > cached pages from the filesystem (i.e. invalidate and free them),
> > yet they are apparrently still accounted as being on the
> > active/inactive LRU.
> > 
> > Reboot, then run dbench for a minute:
> > 
> > $ sudo mkfs.xfs -f /dev/pmem1
> > meta-data=/dev/pmem1             isize=512    agcount=4, agsize=524288 blks
> >          =                       sectsz=4096  attr=2, projid32bit=1
> >          =                       crc=1        finobt=1, sparse=0
> > data     =                       bsize=4096   blocks=2097152, imaxpct=25
> >          =                       sunit=0      swidth=0 blks
> > naming   =version 2              bsize=4096   ascii-ci=0 ftype=1
> > log      =internal log           bsize=4096   blocks=2560, version=2
> >          =                       sectsz=4096  sunit=1 blks, lazy-count=1
> > realtime =none                   extsz=4096   blocks=0, rtextents=0
> > $ sudo mount /dev/pmem1 /mnt/scratch
> > $ sudo dbench -t 60 -D /mnt/scratch/ 16
> > dbench version 4.00 - Copyright Andrew Tridgell 1999-2004
> > 
> 
> Is there any chance this is related to pmem1?

Nope, just reproduced it on /dev/vdc to confirm.

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com