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Re: [Qemu-devel] [QEMU 3/7] Add the hmp and qmp interface for dropping c

From: Li, Liang Z
Subject: Re: [Qemu-devel] [QEMU 3/7] Add the hmp and qmp interface for dropping cache
Date: Mon, 13 Jun 2016 13:50:10 +0000

> Because writing to this file is a nondestructive operation and dirty objects 
> are
> not freeable, the user should run sync(1) first.
> [/quote]
> IOW, by 'slab' you mean dentries and inodes ?

> > +##
> > +{ 'command': 'balloon_drop_cache', 'data': {'value': 'DropCacheType'}
> > +}
> Also, as noted in the man page quote above, it is recommended to call
> sync() to minimise dirty pages. Should we have a way to request a sync as
> part of this monitor command.
> More generally, it feels like this is taking as down a path towards actively
> managing the guest kernel VM from the host. Is this really a path we want to
> be going down, given that its going to take us into increasing non-portable
> concepts which are potentially different for each guest OS kernel.  Is this
> drop caches feature at all applicable to Windows, OS-X, *BSD guest OS impls
> of the balloon driver ? If it is applicable, are the 3 fixed constants you've


> defined at all useful to those other OS ?

Maybe they are not.  
I agree that there are too Linux specific.  And I did more than needed.
Actually, I just want to drop the clean cache, do more than that is too heavy
and no good for performance.

> I'm warying of us taking a design path which is so Linux specific it isn't 
> useful
> elsewhere. IOW, just because we can do this, doesn't mean we should do
> this...



> Regards,
> Daniel
> --
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