| Message ID | 20191209194305.20828-2-sjpark@amazon.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | xenbus/backend: Add a memory pressure handler callback | expand |
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
On Tue, Dec 10, 2019 at 7:11 AM Jürgen Groß <jgross@suse.com> wrote: > > 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? Yes, of course. Will do with the next version. Thanks, SeongJae Park > > Block maintainers, would you be fine with me carrying this series > through the Xen tree? > > > Juergen
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); Oh, sorry for first requesting you to add the domid as a parameter, but now I realize this could be handled in the xenbus driver, as struct xenbus_device already contains the otherend_id. Would you mind dropping the parameter again, please? Juergen
On Tue, Dec 10, 2019 at 7:23 AM Jürgen Groß <jgross@suse.com> wrote: > > 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); > > Oh, sorry for first requesting you to add the domid as a parameter, > but now I realize this could be handled in the xenbus driver, as > struct xenbus_device already contains the otherend_id. > > Would you mind dropping the parameter again, please? Oh, I also missed it! Will do! Thanks, SeongJae Park > > > Juergen
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); }; static inline struct xenbus_driver *to_xenbus_driver(struct device_driver *drv)