[virtio-dev] [PATCH] content: document balloon memory statistics

[virtio-dev] [PATCH] content: document balloon memory statistics

[Tomáš Golembiovský]

Linux kernel provides some balloon memory statistics that were not
included in the specs. Include them to avoid any ID clashes in the
future.

Signed-off-by: Tomáš Golembiovský <tgolembi@redhat.com>
---
 content.tex | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/content.tex b/content.tex
index c7ef7fd..74d351c 100644
--- a/content.tex
+++ b/content.tex
@@ -5028,6 +5028,8 @@ struct virtio_balloon_stat {
 #define VIRTIO_BALLOON_S_MINFLT   3
 #define VIRTIO_BALLOON_S_MEMFREE  4
 #define VIRTIO_BALLOON_S_MEMTOT   5
+#define VIRTIO_BALLOON_S_AVAIL    6
+#define VIRTIO_BALLOON_S_CACHES   7
         le16 tag;
         le64 val;
 } __attribute__((packed));
@@ -5109,6 +5111,12 @@ first buffer.
 
 \item[VIRTIO_BALLOON_S_MEMTOT (5)] The total amount of memory available
   (in bytes).
+
+\item[VIRTIO_BALLOON_S_AVAIL (6)] An estimate of how much memory is available
+  (in bytes) for starting new applications, without pushing the system to swap.
+
+\item[VIRTIO_BALLOON_S_CACHES (7)] The amount of memory currently used for
+  caching files and other data from disk (in bytes).
 \end{description}
 
 \section{SCSI Host Device}\label{sec:Device Types / SCSI Host Device}
-- 
2.16.1


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Re: [virtio-dev] [PATCH] content: document balloon memory statistics

[Stefan Hajnoczi]

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On Mon, Feb 19, 2018 at 02:10:29PM +0100, Tomáš Golembiovský wrote:
> +\item[VIRTIO_BALLOON_S_CACHES (7)] The amount of memory currently used for
> +  caching files and other data from disk (in bytes).
>  \end{description}

This one is somewhat vague.  I'm not sure if it means guest page cache
specifically or something more general.

On the other hand, the numbers tend to be OS specific...

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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Re: [virtio-dev] [PATCH] content: document balloon memory statistics

[Tomáš Golembiovský]

On Tue, 20 Feb 2018 17:15:44 +0000
Stefan Hajnoczi <stefanha@redhat.com> wrote:

> On Mon, Feb 19, 2018 at 02:10:29PM +0100, Tomáš Golembiovský wrote:
> > +\item[VIRTIO_BALLOON_S_CACHES (7)] The amount of memory currently used for
> > +  caching files and other data from disk (in bytes).
> >  \end{description}  
> 
> This one is somewhat vague.  I'm not sure if it means guest page cache
> specifically or something more general.
> 
> On the other hand, the numbers tend to be OS specific...

We should come up with a definition that is as definite as possible
while leaving room for all systems to substitute a value that is
natively available. So if anyone has a better formulation then please
advise. The original intent was not to create a Linux specific field.

On Linux the value corresponds to Buffers + Cached + SwapCached memory
stats. Correct me if I'm wrong but that should be all clean pages that
have a counterpart on disk and can be quickly reclaimed and used for
something else (without additional IO).

On Windows this roughly corresponds to the standby list. Or maybe
standby list plus something else. I suppose there may be some
alternative on BSD too.

    Tomas


-- 
Tomáš Golembiovský <tgolembi@redhat.com>

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Re: [virtio-dev] [PATCH] content: document balloon memory statistics

[Stefan Hajnoczi]

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On Wed, Feb 21, 2018 at 12:11:35AM +0100, Tomáš Golembiovský wrote:
> On Tue, 20 Feb 2018 17:15:44 +0000
> Stefan Hajnoczi <stefanha@redhat.com> wrote:
> 
> > On Mon, Feb 19, 2018 at 02:10:29PM +0100, Tomáš Golembiovský wrote:
> > > +\item[VIRTIO_BALLOON_S_CACHES (7)] The amount of memory currently used for
> > > +  caching files and other data from disk (in bytes).
> > >  \end{description}  
> > 
> > This one is somewhat vague.  I'm not sure if it means guest page cache
> > specifically or something more general.
> > 
> > On the other hand, the numbers tend to be OS specific...
> 
> We should come up with a definition that is as definite as possible
> while leaving room for all systems to substitute a value that is
> natively available. So if anyone has a better formulation then please
> advise. The original intent was not to create a Linux specific field.
> 
> On Linux the value corresponds to Buffers + Cached + SwapCached memory
> stats. Correct me if I'm wrong but that should be all clean pages that
> have a counterpart on disk and can be quickly reclaimed and used for
> something else (without additional IO).

Thanks for clarifying.  Based on what you posted, how about:

"The amount of memory, in bytes, that can be quickly reclaimed without
additional I/O.  Typically these pages are used for caching files from
disk."

?

> On Windows this roughly corresponds to the standby list. Or maybe
> standby list plus something else. I suppose there may be some
> alternative on BSD too.
> 
>     Tomas
> 
> 
> -- 
> Tomáš Golembiovský <tgolembi@redhat.com>

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Re: [virtio-dev] [PATCH] content: document balloon memory statistics

[Tomáš Golembiovský]

On Wed, 21 Feb 2018 11:33:28 +0000
Stefan Hajnoczi <stefanha@redhat.com> wrote:

> On Wed, Feb 21, 2018 at 12:11:35AM +0100, Tomáš Golembiovský wrote:
> > On Tue, 20 Feb 2018 17:15:44 +0000
> > Stefan Hajnoczi <stefanha@redhat.com> wrote:
> > 
> > > On Mon, Feb 19, 2018 at 02:10:29PM +0100, Tomáš Golembiovský wrote:
> > > > +\item[VIRTIO_BALLOON_S_CACHES (7)] The amount of memory currently used for
> > > > +  caching files and other data from disk (in bytes).
> > > >  \end{description}  
> > > 
> > > This one is somewhat vague.  I'm not sure if it means guest page cache
> > > specifically or something more general.
> > > 
> > > On the other hand, the numbers tend to be OS specific...
> > 
> > We should come up with a definition that is as definite as possible
> > while leaving room for all systems to substitute a value that is
> > natively available. So if anyone has a better formulation then please
> > advise. The original intent was not to create a Linux specific field.
> > 
> > On Linux the value corresponds to Buffers + Cached + SwapCached memory
> > stats. Correct me if I'm wrong but that should be all clean pages that
> > have a counterpart on disk and can be quickly reclaimed and used for
> > something else (without additional IO).
> 
> Thanks for clarifying.  Based on what you posted, how about:
> 
> "The amount of memory, in bytes, that can be quickly reclaimed without
> additional I/O.  Typically these pages are used for caching files from
> disk."
> 
> ?

Sounds reasonable, thanks

    Tomas


> 
> > On Windows this roughly corresponds to the standby list. Or maybe
> > standby list plus something else. I suppose there may be some
> > alternative on BSD too.
> > 
> >     Tomas
> > 
> > 
> > -- 
> > Tomáš Golembiovský <tgolembi@redhat.com>


-- 
Tomáš Golembiovský <tgolembi@redhat.com>

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Re: [virtio-dev] [PATCH] content: document balloon memory statistics

[Michael S. Tsirkin]

On Wed, Feb 21, 2018 at 06:44:17PM +0100, Tomáš Golembiovský wrote:
> On Wed, 21 Feb 2018 11:33:28 +0000
> Stefan Hajnoczi <stefanha@redhat.com> wrote:
> 
> > On Wed, Feb 21, 2018 at 12:11:35AM +0100, Tomáš Golembiovský wrote:
> > > On Tue, 20 Feb 2018 17:15:44 +0000
> > > Stefan Hajnoczi <stefanha@redhat.com> wrote:
> > > 
> > > > On Mon, Feb 19, 2018 at 02:10:29PM +0100, Tomáš Golembiovský wrote:
> > > > > +\item[VIRTIO_BALLOON_S_CACHES (7)] The amount of memory currently used for
> > > > > +  caching files and other data from disk (in bytes).
> > > > >  \end{description}  
> > > > 
> > > > This one is somewhat vague.  I'm not sure if it means guest page cache
> > > > specifically or something more general.
> > > > 
> > > > On the other hand, the numbers tend to be OS specific...
> > > 
> > > We should come up with a definition that is as definite as possible
> > > while leaving room for all systems to substitute a value that is
> > > natively available. So if anyone has a better formulation then please
> > > advise. The original intent was not to create a Linux specific field.
> > > 
> > > On Linux the value corresponds to Buffers + Cached + SwapCached memory
> > > stats. Correct me if I'm wrong but that should be all clean pages that
> > > have a counterpart on disk and can be quickly reclaimed and used for
> > > something else (without additional IO).
> > 
> > Thanks for clarifying.  Based on what you posted, how about:
> > 
> > "The amount of memory, in bytes, that can be quickly reclaimed without
> > additional I/O.  Typically these pages are used for caching files from
> > disk."
> > 
> > ?
> 
> Sounds reasonable, thanks
> 
>     Tomas

OK - will you post v2 then?

> 
> > 
> > > On Windows this roughly corresponds to the standby list. Or maybe
> > > standby list plus something else. I suppose there may be some
> > > alternative on BSD too.
> > > 
> > >     Tomas
> > > 
> > > 
> > > -- 
> > > Tomáš Golembiovský <tgolembi@redhat.com>
> 
> 
> -- 
> Tomáš Golembiovský <tgolembi@redhat.com>

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Re: [virtio-dev] [PATCH] content: document balloon memory statistics

[Tomáš Golembiovský]

On Tue, 27 Feb 2018 21:56:04 +0200
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Wed, Feb 21, 2018 at 06:44:17PM +0100, Tomáš Golembiovský wrote:
> > On Wed, 21 Feb 2018 11:33:28 +0000
> > Stefan Hajnoczi <stefanha@redhat.com> wrote:
> >   
> > > On Wed, Feb 21, 2018 at 12:11:35AM +0100, Tomáš Golembiovský wrote:  
> > > > On Tue, 20 Feb 2018 17:15:44 +0000
> > > > Stefan Hajnoczi <stefanha@redhat.com> wrote:
> > > >   
> > > > > On Mon, Feb 19, 2018 at 02:10:29PM +0100, Tomáš Golembiovský wrote:  
> > > > > > +\item[VIRTIO_BALLOON_S_CACHES (7)] The amount of memory currently used for
> > > > > > +  caching files and other data from disk (in bytes).
> > > > > >  \end{description}    
> > > > > 
> > > > > This one is somewhat vague.  I'm not sure if it means guest page cache
> > > > > specifically or something more general.
> > > > > 
> > > > > On the other hand, the numbers tend to be OS specific...  
> > > > 
> > > > We should come up with a definition that is as definite as possible
> > > > while leaving room for all systems to substitute a value that is
> > > > natively available. So if anyone has a better formulation then please
> > > > advise. The original intent was not to create a Linux specific field.
> > > > 
> > > > On Linux the value corresponds to Buffers + Cached + SwapCached memory
> > > > stats. Correct me if I'm wrong but that should be all clean pages that
> > > > have a counterpart on disk and can be quickly reclaimed and used for
> > > > something else (without additional IO).  
> > > 
> > > Thanks for clarifying.  Based on what you posted, how about:
> > > 
> > > "The amount of memory, in bytes, that can be quickly reclaimed without
> > > additional I/O.  Typically these pages are used for caching files from
> > > disk."
> > > 
> > > ?  
> > 
> > Sounds reasonable, thanks
> > 
> >     Tomas  
> 
> OK - will you post v2 then?

I already have:
https://lists.oasis-open.org/archives/virtio-dev/201802/msg00141.html

> 
> >   
> > >   
> > > > On Windows this roughly corresponds to the standby list. Or maybe
> > > > standby list plus something else. I suppose there may be some
> > > > alternative on BSD too.
> > > > 
> > > >     Tomas
> > > > 
> > > > 
> > > > -- 
> > > > Tomáš Golembiovský <tgolembi@redhat.com>  
> > 
> > 
> > -- 
> > Tomáš Golembiovský <tgolembi@redhat.com>  


-- 
Tomáš Golembiovský <tgolembi@redhat.com>

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