diff options
| -rw-r--r-- | content.tex | 31 |
1 files changed, 27 insertions, 4 deletions
diff --git a/content.tex b/content.tex index b1cd7bf..9f65748 100644 --- a/content.tex +++ b/content.tex @@ -4390,6 +4390,9 @@ guest memory statistics to the host. \item[VIRTIO_BALLOON_F_STATS_VQ (1)] A virtqueue for reporting guest memory statistics is present. +\item[VIRTIO_BALLOON_F_DEFLATE_ON_OOM (2) ] Deflate balloon on + guest out of memory condition. + \end{description} \drivernormative{\subsubsection}{Feature bits}{Device Types / Memory Balloon Device / Feature bits} @@ -4449,8 +4452,10 @@ The device initialization process is outlined below: \subsection{Device Operation}\label{sec:Device Types / Memory Balloon Device / Device Operation} -The device is driven by the receipt of a -configuration change interrupt. +The device is driven either by the receipt of a configuration +change interrupt, or by changing guest memory needs, such as +performing memory compaction or responding to out of memory +conditions. \begin{enumerate} \item \field{num_pages} configuration field is examined. If this is @@ -4489,10 +4494,25 @@ requests by using the descriptor. \drivernormative{\subsubsection}{Device Operation}{Device Types / Memory Balloon Device / Device Operation} The driver SHOULD supply pages to the balloon when \field{num_pages} is -greater than \field{actual}. +greater than the actual number of pages in the balloon. The driver MAY use pages from the balloon when \field{num_pages} is -less than \field{actual}. +less than the actual number of pages in the balloon. + +The driver MAY supply pages to the balloon when \field{num_pages} is +greater than or equal to the actual number of pages in the balloon. + +If VIRTIO_BALLOON_F_DEFLATE_ON_OOM has not been negotiated, the +driver MUST NOT use pages from the balloon when \field{num_pages} +is less than or equal to the actual number of pages in the +balloon. + +If VIRTIO_BALLOON_F_DEFLATE_ON_OOM has been negotiated, the +driver MAY use pages from the balloon when \field{num_pages} +is less than or equal to the actual number of pages in the +balloon if this is required for system stability +(e.g. if memory is required by applications running within + the guest). The driver MUST use the deflateq to inform the device of pages that it wants to use from the balloon. @@ -4517,6 +4537,9 @@ request. The driver MUST update \field{actual} after changing the number of pages in the balloon. +The driver MAY update \field{actual} once after multiple +inflate and deflate operations. + \devicenormative{\subsubsection}{Device Operation}{Device Types / Memory Balloon Device / Device Operation} The device MAY modify the contents of a page in the balloon |