search for: virtio_balloon_oom_notify

Two fixes for issues I stumbled over while working on patch #3. Switch back to the good ol' OOM handler for VIRTIO_BALLOON_F_DEFLATE_ON_OOM as the switch to the shrinker introduce some undesired side effects. Keep the shrinker in place to handle VIRTIO_BALLOON_F_FREE_PAGE_HINT. Lengthy discussion under [1]. I tested with QEMU and "deflate-on-oom=on". Works as expected. Did not test

...mmit 71994620bb25 ("virtio_balloon: replace oom notifier with shrinker"), don't add a moodule parameter to configure the number of pages to deflate on OOM. Can be re-added if really needed. Also, pay attention that leak_balloon() returns the number of 4k pages - convert it properly in virtio_balloon_oom_notify(). Testing done by Tyler for future reference: Test setup: VM with 16 CPU, 64GB RAM. Running Debian 10. We have a 42 GB file full of random bytes that we continually cat to /dev/null. This fills the page cache as the file is read. Meanwhile we trigger the balloon to inflate, with a target...

...mmit 71994620bb25 ("virtio_balloon: replace oom notifier with shrinker"), don't add a moodule parameter to configure the number of pages to deflate on OOM. Can be re-added if really needed. Also, pay attention that leak_balloon() returns the number of 4k pages - convert it properly in virtio_balloon_oom_notify(). Testing done by Tyler for future reference: Test setup: VM with 16 CPU, 64GB RAM. Running Debian 10. We have a 42 GB file full of random bytes that we continually cat to /dev/null. This fills the page cache as the file is read. Meanwhile we trigger the balloon to inflate, with a target...

@Andrew, as this fix is based on free page reporting, can this go through your tree? Patch #1 contains a proper description. v3 -> v4: - Add Ack from David Rientjes - Minor tweaks to test details in the patch description v2 -> v3: - Use vb->vdev instead of vdev in all feature checks. We'll clean the other ones up later. - Add one empty line virtballoon_probe() to make it look

...quot;virtio_balloon: replace oom > notifier with shrinker"), don't add a moodule parameter to configure the > number of pages to deflate on OOM. Can be re-added if really needed. > Also, pay attention that leak_balloon() returns the number of 4k pages - > convert it properly in virtio_balloon_oom_notify(). > > Note1: using the OOM handler is frowned upon, but it really is what we > need for this feature. > > Note2: without VIRTIO_BALLOON_F_MUST_TELL_HOST (iow, always with QEMU) we > could actually skip sending deflation requests to our hypervisor, > making...

...quot;virtio_balloon: replace oom > notifier with shrinker"), don't add a moodule parameter to configure the > number of pages to deflate on OOM. Can be re-added if really needed. > Also, pay attention that leak_balloon() returns the number of 4k pages - > convert it properly in virtio_balloon_oom_notify(). > > Note1: using the OOM handler is frowned upon, but it really is what we > need for this feature. > > Note2: without VIRTIO_BALLOON_F_MUST_TELL_HOST (iow, always with QEMU) we > could actually skip sending deflation requests to our hypervisor, > making...

...mmit 71994620bb25 ("virtio_balloon: replace oom notifier with shrinker"), don't add a moodule parameter to configure the number of pages to deflate on OOM. Can be re-added if really needed. Also, pay attention that leak_balloon() returns the number of 4k pages - convert it properly in virtio_balloon_oom_notify(). Testing done by Tyler for future reference: Test setup: VM with 16 CPU, 64GB RAM. Running Debian 10. We have a 42 GB file full of random bytes that we continually cat to /dev/null. This fills the page cache as the file is read. Meanwhile we trigger the balloon to inflate, with a target...

...mmit 71994620bb25 ("virtio_balloon: replace oom notifier with shrinker"), don't add a moodule parameter to configure the number of pages to deflate on OOM. Can be re-added if really needed. Also, pay attention that leak_balloon() returns the number of 4k pages - convert it properly in virtio_balloon_oom_notify(). Testing done by Tyler for future reference: Test setup: VM with 16 CPU, 64GB RAM. Running Debian 10. We have a 42 GB file full of random bytes that we continually cat to /dev/null. This fills the page cache as the file is read. Meanwhile we trigger the balloon to inflate, with a target...

...* still to be processed by the host. >> + */ >> + err = virtio_balloon_register_shrinker(vb); >> + if (err) >> + goto out_del_balloon_wq; >> } >> + if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) { >> + vb->oom_nb.notifier_call = virtio_balloon_oom_notify; >> + vb->oom_nb.priority = VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY; >> + err = register_oom_notifier(&vb->oom_nb); >> + if (err < 0) >> + goto out_unregister_shrinker; >> + } >> + > > > Let's decide whether we want an empty line after...

...* still to be processed by the host. >> + */ >> + err = virtio_balloon_register_shrinker(vb); >> + if (err) >> + goto out_del_balloon_wq; >> } >> + if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) { >> + vb->oom_nb.notifier_call = virtio_balloon_oom_notify; >> + vb->oom_nb.priority = VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY; >> + err = register_oom_notifier(&vb->oom_nb); >> + if (err < 0) >> + goto out_unregister_shrinker; >> + } >> + > > > Let's decide whether we want an empty line after...

...quot;virtio_balloon: replace oom > notifier with shrinker"), don't add a moodule parameter to configure the > number of pages to deflate on OOM. Can be re-added if really needed. > Also, pay attention that leak_balloon() returns the number of 4k pages - > convert it properly in virtio_balloon_oom_notify(). > > Note1: using the OOM handler is frowned upon, but it really is what we > need for this feature. > > Note2: without VIRTIO_BALLOON_F_MUST_TELL_HOST (iow, always with QEMU) we > could actually skip sending deflation requests to our hypervisor, > maki...

...mmit 71994620bb25 ("virtio_balloon: replace oom notifier with shrinker"), don't add a moodule parameter to configure the number of pages to deflate on OOM. Can be re-added if really needed. Also, pay attention that leak_balloon() returns the number of 4k pages - convert it properly in virtio_balloon_oom_notify(). Note1: using the OOM handler is frowned upon, but it really is what we need for this feature. Note2: without VIRTIO_BALLOON_F_MUST_TELL_HOST (iow, always with QEMU) we could actually skip sending deflation requests to our hypervisor, making the OOM path *very* simple. Besi...

...ommit 71994620bb25 ("virtio_balloon: replace oom notifier with shrinker"), don't add a module parameter to configure the number of pages to deflate on OOM. Can be re-added if really needed. Also, pay attention that leak_balloon() returns the number of 4k pages - convert it properly in virtio_balloon_oom_notify(). Testing done by Tyler for future reference: Test setup: VM with 16 CPU, 64GB RAM. Running Debian 10. We have a 42 GB file full of random bytes that we continually cat to /dev/null. This fills the page cache as the file is read. Meanwhile, we trigger the balloon to inflate, with a target...

...quot;virtio_balloon: replace oom > notifier with shrinker"), don't add a moodule parameter to configure the > number of pages to deflate on OOM. Can be re-added if really needed. > Also, pay attention that leak_balloon() returns the number of 4k pages - > convert it properly in virtio_balloon_oom_notify(). > > Testing done by Tyler for future reference: > Test setup: VM with 16 CPU, 64GB RAM. Running Debian 10. We have a 42 > GB file full of random bytes that we continually cat to /dev/null. > This fills the page cache as the file is read. Meanwhile we trigger > the ball...

...mmit 71994620bb25 ("virtio_balloon: replace oom notifier with shrinker"), don't add a moodule parameter to configure the number of pages to deflate on OOM. Can be re-added if really needed. Also, pay attention that leak_balloon() returns the number of 4k pages - convert it properly in virtio_balloon_oom_notify(). Note1: using the OOM handler is frowned upon, but it really is what we need for this feature. Note2: without VIRTIO_BALLOON_F_MUST_TELL_HOST (iow, always with QEMU) we could actually skip sending deflation requests to our hypervisor, making the OOM path *very* simple. Besi...

...mmit 71994620bb25 ("virtio_balloon: replace oom notifier with shrinker"), don't add a moodule parameter to configure the number of pages to deflate on OOM. Can be re-added if really needed. Also, pay attention that leak_balloon() returns the number of 4k pages - convert it properly in virtio_balloon_oom_notify(). Note1: using the OOM handler is frowned upon, but it really is what we need for this feature. Note2: without VIRTIO_BALLOON_F_MUST_TELL_HOST (iow, always with QEMU) we could actually skip sending deflation requests to our hypervisor, making the OOM path *very* simple. Besi...

...t;linux/mount.h> @@ -28,9 +27,7 @@ */ #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT) #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256 -/* Maximum number of (4k) pages to deflate on OOM notifications. */ -#define VIRTIO_BALLOON_OOM_NR_PAGES 256 -#define VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY 80 +#define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \ __GFP_NOMEMALLOC) @@ -115,11 +112,8 @@ struct virtio_balloon { /* Memory statistics */ struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR]; - /...

...#define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT) #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256 -#define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80 +/* Maximum number of (4k) pages to deflate on OOM notifications. */ +#define VIRTIO_BALLOON_OOM_NR_PAGES 256 +#define VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY 80 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \ __GFP_NOMEMALLOC) @@ -112,8 +115,11 @@ struct virtio_balloon { /* Memory statistics */ struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR]; - /* To register a shrinker to shrink memory up...

...a patch virtio-balloon: deflate up to oom_pages on OOM by Wei Wang to try to fix it: https://lore.kernel.org/r/1508500466-21165-3-git-send-email-wei.w.wang at intel.com but this was dropped. > Also, pay attention that leak_balloon() returns the number of 4k pages - > convert it properly in virtio_balloon_oom_notify(). Oh. So it was returning a wrong value originally (before 71994620bb25). However what really matters for notifiers is whether the value is 0 - whether we made progress. So it's cosmetic. > Note1: using the OOM handler is frowned upon, but it really is what we > need for this fe...

...a patch virtio-balloon: deflate up to oom_pages on OOM by Wei Wang to try to fix it: https://lore.kernel.org/r/1508500466-21165-3-git-send-email-wei.w.wang at intel.com but this was dropped. > Also, pay attention that leak_balloon() returns the number of 4k pages - > convert it properly in virtio_balloon_oom_notify(). Oh. So it was returning a wrong value originally (before 71994620bb25). However what really matters for notifiers is whether the value is 0 - whether we made progress. So it's cosmetic. > Note1: using the OOM handler is frowned upon, but it really is what we > need for this fe...