Re: [PATCH v4] xen: speed up grant-table reclaim

[Juergen Gross <jgross@xxxxxxxx>]

On 26.07.23 18:52, Demi Marie Obenour wrote:
> When a grant entry is still in use by the remote domain, Linux must put
> it on a deferred list.  Normally, this list is very short, because
> the PV network and block protocols expect the backend to unmap the grant
> first.  However, Qubes OS's GUI protocol is subject to the constraints
> of the X Window System, and as such winds up with the frontend unmapping
> the window first.  As a result, the list can grow very large, resulting
> in a massive memory leak and eventual VM freeze.
>
> To partially solve this problem, make the number of entries that the VM
> will attempt to free at each iteration tunable.  The default is still
> 10, but it can be overridden via a module parameter.
>
> This is Cc: stable because (when combined with appropriate userspace
> changes) it fixes a severe performance and stability problem for Qubes
> OS users.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>


Juergen

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