Messages in this thread | | | Subject | Re: [PATCH v4 1/2] xenbus/backend: Add memory pressure handler callback | From | Jürgen Groß <> | Date | Tue, 10 Dec 2019 07:11:49 +0100 |
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On 09.12.19 20:43, SeongJae Park wrote: > From: SeongJae Park <sjpark@amazon.de> > > Granting pages consumes backend system memory. In systems configured > with insufficient spare memory for those pages, it can cause a memory > pressure situation. However, finding the optimal amount of the spare > memory is challenging for large systems having dynamic resource > utilization patterns. Also, such a static configuration might lacks a > flexibility. > > To mitigate such problems, this commit adds a memory reclaim callback to > 'xenbus_driver'. Using this facility, 'xenbus' would be able to monitor > a memory pressure and request specific domains of specific backend > drivers which causing the given pressure to voluntarily release its > memory. > > That said, this commit simply requests every callback registered driver > to release its memory for every domain, rather than issueing the > requests to the drivers and domain in charge. Such things would be a > future work. Also, this commit focuses on memory only. However, it > would be ablt to be extended for general resources. > > Signed-off-by: SeongJae Park <sjpark@amazon.de> > --- > drivers/xen/xenbus/xenbus_probe_backend.c | 31 +++++++++++++++++++++++ > include/xen/xenbus.h | 1 + > 2 files changed, 32 insertions(+) > > diff --git a/drivers/xen/xenbus/xenbus_probe_backend.c b/drivers/xen/xenbus/xenbus_probe_backend.c > index b0bed4faf44c..cd5fd1cd8de3 100644 > --- a/drivers/xen/xenbus/xenbus_probe_backend.c > +++ b/drivers/xen/xenbus/xenbus_probe_backend.c > @@ -248,6 +248,34 @@ static int backend_probe_and_watch(struct notifier_block *notifier, > return NOTIFY_DONE; > } > > +static int xenbus_backend_reclaim(struct device *dev, void *data) > +{ > + struct xenbus_driver *drv; > + if (!dev->driver) > + return -ENOENT; > + drv = to_xenbus_driver(dev->driver); > + if (drv && drv->reclaim) > + drv->reclaim(to_xenbus_device(dev), DOMID_INVALID); > + return 0; > +} > + > +/* > + * Returns 0 always because we are using shrinker to only detect memory > + * pressure. > + */ > +static unsigned long xenbus_backend_shrink_count(struct shrinker *shrinker, > + struct shrink_control *sc) > +{ > + bus_for_each_dev(&xenbus_backend.bus, NULL, NULL, > + xenbus_backend_reclaim); > + return 0; > +} > + > +static struct shrinker xenbus_backend_shrinker = { > + .count_objects = xenbus_backend_shrink_count, > + .seeks = DEFAULT_SEEKS, > +}; > + > static int __init xenbus_probe_backend_init(void) > { > static struct notifier_block xenstore_notifier = { > @@ -264,6 +292,9 @@ static int __init xenbus_probe_backend_init(void) > > register_xenstore_notifier(&xenstore_notifier); > > + if (register_shrinker(&xenbus_backend_shrinker)) > + pr_warn("shrinker registration failed\n"); > + > return 0; > } > subsys_initcall(xenbus_probe_backend_init); > diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h > index 869c816d5f8c..52aaf4f78400 100644 > --- a/include/xen/xenbus.h > +++ b/include/xen/xenbus.h > @@ -104,6 +104,7 @@ struct xenbus_driver { > struct device_driver driver; > int (*read_otherend_details)(struct xenbus_device *dev); > int (*is_ready)(struct xenbus_device *dev); > + unsigned (*reclaim)(struct xenbus_device *dev, domid_t domid);
Can you please add a comment here regarding semantics of specifying DOMID_INVALID as domid?
Block maintainers, would you be fine with me carrying this series through the Xen tree?
Juergen
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