Re: [PATCH v2 1/1] virtio_balloon: include buffers and cached memory statistics

["Tomáš Golembiovský" <tgolembi@redhat.com>]

ping

+Gil, +Amnon... could you maybe aid in reviewing the patch, please?


    Tomas

On Sun, 22 Oct 2017 20:05:57 +0200
Tomáš Golembiovský <tgolembi@redhat.com> wrote:

> On Thu, 19 Oct 2017 16:12:20 +0300
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
> 
> > On Thu, Sep 21, 2017 at 02:55:41PM +0200, Tomáš Golembiovský wrote:  
> > > Add a new fields, VIRTIO_BALLOON_S_BUFFERS and VIRTIO_BALLOON_S_CACHED,
> > > to virtio_balloon memory statistics protocol. The values correspond to
> > > 'Buffers' and 'Cached' in /proc/meminfo.
> > > 
> > > To be able to compute the value of 'Cached' memory it is necessary to
> > > export total_swapcache_pages() to modules.
> > > 
> > > Signed-off-by: Tomáš Golembiovský <tgolembi@redhat.com>  
> > 
> > Does 'Buffers' actually make sense? It's a temporary storage -
> > wouldn't it be significantly out of date by the time
> > host receives it?  
> 
> That would be best answered by somebody from kernel. But my personal
> opinion is that it would not be out of date. The amount of memory
> dedicated to Buffers does not seem to fluctuate too much.
> 
>     Tomas
> 
> 
> > > ---
> > >  drivers/virtio/virtio_balloon.c     | 11 +++++++++++
> > >  include/uapi/linux/virtio_balloon.h |  4 +++-
> > >  mm/swap_state.c                     |  1 +
> > >  3 files changed, 15 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> > > index f0b3a0b9d42f..c2558ec47a62 100644
> > > --- a/drivers/virtio/virtio_balloon.c
> > > +++ b/drivers/virtio/virtio_balloon.c
> > > @@ -244,12 +244,19 @@ static unsigned int update_balloon_stats(struct virtio_balloon *vb)
> > >  	struct sysinfo i;
> > >  	unsigned int idx = 0;
> > >  	long available;
> > > +	long cached;
> > >  
> > >  	all_vm_events(events);
> > >  	si_meminfo(&i);
> > >  
> > >  	available = si_mem_available();
> > >  
> > > +	cached = global_node_page_state(NR_FILE_PAGES) -
> > > +			total_swapcache_pages() - i.bufferram;
> > > +	if (cached < 0)
> > > +		cached = 0;
> > > +
> > > +
> > >  #ifdef CONFIG_VM_EVENT_COUNTERS
> > >  	update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
> > >  				pages_to_bytes(events[PSWPIN]));
> > > @@ -264,6 +271,10 @@ static unsigned int update_balloon_stats(struct virtio_balloon *vb)
> > >  				pages_to_bytes(i.totalram));
> > >  	update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
> > >  				pages_to_bytes(available));
> > > +	update_stat(vb, idx++, VIRTIO_BALLOON_S_BUFFERS,
> > > +				pages_to_bytes(i.bufferram));
> > > +	update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHED,
> > > +				pages_to_bytes(cached));
> > >  
> > >  	return idx;
> > >  }
> > > diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
> > > index 343d7ddefe04..d5dc8a56a497 100644
> > > --- a/include/uapi/linux/virtio_balloon.h
> > > +++ b/include/uapi/linux/virtio_balloon.h
> > > @@ -52,7 +52,9 @@ struct virtio_balloon_config {
> > >  #define VIRTIO_BALLOON_S_MEMFREE  4   /* Total amount of free memory */
> > >  #define VIRTIO_BALLOON_S_MEMTOT   5   /* Total amount of memory */
> > >  #define VIRTIO_BALLOON_S_AVAIL    6   /* Available memory as in /proc */
> > > -#define VIRTIO_BALLOON_S_NR       7
> > > +#define VIRTIO_BALLOON_S_BUFFERS  7   /* Buffers memory as in /proc */
> > > +#define VIRTIO_BALLOON_S_CACHED   8   /* Cached memory as in /proc */
> > > +#define VIRTIO_BALLOON_S_NR       9
> > >  
> > >  /*
> > >   * Memory statistics structure.
> > > diff --git a/mm/swap_state.c b/mm/swap_state.c
> > > index 71ce2d1ccbf7..f3a4ff7d6c52 100644
> > > --- a/mm/swap_state.c
> > > +++ b/mm/swap_state.c
> > > @@ -95,6 +95,7 @@ unsigned long total_swapcache_pages(void)
> > >  	rcu_read_unlock();
> > >  	return ret;
> > >  }
> > > +EXPORT_SYMBOL_GPL(total_swapcache_pages);
> > >  
> > >  static atomic_t swapin_readahead_hits = ATOMIC_INIT(4);  
> > 
> > Need an ack from MM crowd on that.
> >   
> > > -- 
> > > 2.14.1  
> 
> 
> -- 
> Tomáš Golembiovský <tgolembi@redhat.com>


-- 
Tomáš Golembiovský <tgolembi@redhat.com>

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