[Devel] [PATCH RHEL7 COMMIT] hv_balloon: Create debugfs file with hyper-v balloon usage information
Konstantin Khorenko
khorenko at virtuozzo.com
Mon Aug 15 16:02:57 MSK 2022
The commit is pushed to "branch-rh7-3.10.0-1160.66.1.vz7.188.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1160.66.1.vz7.188.9
------>
commit f182624db04c3ca254e7e11d6ddd2b8fac0d3655
Author: Alexander Atanasov <alexander.atanasov at virtuozzo.com>
Date: Fri Jul 29 17:48:24 2022 +0300
hv_balloon: Create debugfs file with hyper-v balloon usage information
Allow the guest to know how much it is ballooned by the host.
It is useful when debugging out of memory conditions.
When host gets back memory from the guest it is accounted
as used memory in the guest but the guest have no way to know
how much it is actually ballooned.
Expose current state, flags and max possible memory to the guest.
While at it - fix a 10+ years old typo.
The patch is in the hyperv-next kernel tree:
https://kernel.googlesource.com/pub/scm/linux/kernel/git/hyperv/linux/+/d180e0a1be6cea2b7436fadbd1c96aecdf3c46c7
https://jira.sw.ru/browse/PSBM-140409
Signed-off-by: Alexander Atanasov <alexander.atanasov at virtuozzo.com>
---
arch/x86/include/asm/mshyperv.h | 11 +++
drivers/hv/hv_balloon.c | 173 ++++++++++++++++++++++++++++++++++++++--
2 files changed, 176 insertions(+), 8 deletions(-)
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 4ccad736c78e4..eb90cb14094d3 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -8,6 +8,17 @@
#include <asm/hyperv.h>
#include <asm/nospec-branch.h>
+
+/*
+ * While not explicitly listed in the TLFS, Hyper-V always runs with a page size
+ * of 4096. These definitions are used when communicating with Hyper-V using
+ * guest physical pages and guest physical page addresses, since the guest page
+ * size may not be 4096 on all architectures.
+ */
+#define HV_HYP_PAGE_SHIFT 12
+#define HV_HYP_PAGE_SIZE BIT(HV_HYP_PAGE_SHIFT)
+#define HV_HYP_PAGE_MASK (~(HV_HYP_PAGE_SIZE - 1))
+
/*
* The below CPUID leaves are present if VersionAndFeatures.HypervisorPresent
* is set by CPUID(HVCPUID_VERSION_FEATURES).
diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index fa8ab1d54cf02..9bf30659a9757 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -21,6 +21,7 @@
#include <linux/kernel.h>
#include <linux/jiffies.h>
#include <linux/mman.h>
+#include <linux/debugfs.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/module.h>
@@ -33,6 +34,7 @@
#include <linux/percpu_counter.h>
#include <linux/hyperv.h>
+#include <asm/mshyperv.h>
#define CREATE_TRACE_POINTS
#include "hv_trace_balloon.h"
@@ -253,7 +255,7 @@ struct dm_capabilities_resp_msg {
* num_committed: Committed memory in pages.
* page_file_size: The accumulated size of all page files
* in the system in pages.
- * zero_free: The nunber of zero and free pages.
+ * zero_free: The number of zero and free pages.
* page_file_writes: The writes to the page file in pages.
* io_diff: An indicator of file cache efficiency or page file activity,
* calculated as File Cache Page Fault Count - Page Read Count.
@@ -572,6 +574,11 @@ struct hv_dynmem_device {
* The negotiated version agreed by host.
*/
__u32 version;
+
+ /*
+ * Maximum number of pages that can be hot_add-ed
+ */
+ __u64 max_dynamic_page_count;
};
static struct hv_dynmem_device dm_device;
@@ -1084,6 +1091,7 @@ static void process_info(struct hv_dynmem_device *dm, struct dm_info_msg *msg)
pr_info("Max. dynamic memory size: %llu MB\n",
(*max_page_count) >> (20 - PAGE_SHIFT));
+ dm->max_dynamic_page_count = *max_page_count;
}
break;
@@ -1121,6 +1129,19 @@ static unsigned long compute_balloon_floor(void)
return min_pages;
}
+/*
+ * Compute total committed memory pages
+ */
+
+static unsigned long get_pages_committed(struct hv_dynmem_device *dm)
+{
+ return vm_memory_committed() +
+ dm->num_pages_ballooned +
+ (dm->num_pages_added > dm->num_pages_onlined ?
+ dm->num_pages_added - dm->num_pages_onlined : 0) +
+ compute_balloon_floor();
+}
+
/*
* Post our status as it relates memory pressure to the
* host. Host expects the guests to post this status
@@ -1161,11 +1182,7 @@ static void post_status(struct hv_dynmem_device *dm)
* asking us to balloon them out.
*/
status.num_avail = si_mem_available();
- status.num_committed = vm_memory_committed() +
- dm->num_pages_ballooned +
- (dm->num_pages_added > dm->num_pages_onlined ?
- dm->num_pages_added - dm->num_pages_onlined : 0) +
- compute_balloon_floor();
+ status.num_committed = get_pages_committed(dm);
trace_balloon_status(status.num_avail, status.num_committed,
vm_memory_committed(), dm->num_pages_ballooned,
@@ -1570,6 +1587,142 @@ static void balloon_onchannelcallback(void *context)
}
+static int ballooning_enabled(void)
+{
+ /*
+ * Disable ballooning if the page size is not 4k (HV_HYP_PAGE_SIZE),
+ * since currently it's unclear to us whether an unballoon request can
+ * make sure all page ranges are guest page size aligned.
+ */
+ if (PAGE_SIZE != HV_HYP_PAGE_SIZE) {
+ pr_info("Ballooning disabled because page size is not 4096 bytes\n");
+ return 0;
+ }
+
+ return 1;
+}
+
+static int hot_add_enabled(void)
+{
+ /*
+ * Disable hot add on ARM64, because we currently rely on
+ * memory_add_physaddr_to_nid() to get a node id of a hot add range,
+ * however ARM64's memory_add_physaddr_to_nid() always return 0 and
+ * DM_MEM_HOT_ADD_REQUEST doesn't have the NUMA node information for
+ * add_memory().
+ */
+ if (IS_ENABLED(CONFIG_ARM64)) {
+ pr_info("Memory hot add disabled on ARM64\n");
+ return 0;
+ }
+
+ return 1;
+}
+
+
+/*
+ * DEBUGFS Interface
+ */
+#ifdef CONFIG_DEBUG_FS
+
+/**
+ * hv_balloon_debug_show - shows statistics of balloon operations.
+ * @f: pointer to the &struct seq_file.
+ * @offset: ignored.
+ *
+ * Provides the statistics that can be accessed in hv-balloon in the debugfs.
+ *
+ * Return: zero on success or an error code.
+ */
+static int hv_balloon_debug_show(struct seq_file *f, void *offset)
+{
+ struct hv_dynmem_device *dm = f->private;
+ char *sname;
+
+ seq_printf(f, "%-22s: %u.%u\n", "host_version",
+ DYNMEM_MAJOR_VERSION(dm->version),
+ DYNMEM_MINOR_VERSION(dm->version));
+
+ seq_printf(f, "%-22s:", "capabilities");
+ if (ballooning_enabled())
+ seq_puts(f, " enabled");
+
+ if (hot_add_enabled())
+ seq_puts(f, " hot_add");
+
+ seq_puts(f, "\n");
+
+ seq_printf(f, "%-22s: %u", "state", dm->state);
+ switch (dm->state) {
+ case DM_INITIALIZING:
+ sname = "Initializing";
+ break;
+ case DM_INITIALIZED:
+ sname = "Initialized";
+ break;
+ case DM_BALLOON_UP:
+ sname = "Balloon Up";
+ break;
+ case DM_BALLOON_DOWN:
+ sname = "Balloon Down";
+ break;
+ case DM_HOT_ADD:
+ sname = "Hot Add";
+ break;
+ case DM_INIT_ERROR:
+ sname = "Error";
+ break;
+ default:
+ sname = "Unknown";
+ }
+ seq_printf(f, " (%s)\n", sname);
+
+ /* HV Page Size */
+ seq_printf(f, "%-22s: %ld\n", "page_size", HV_HYP_PAGE_SIZE);
+
+ /* Pages added with hot_add */
+ seq_printf(f, "%-22s: %u\n", "pages_added", dm->num_pages_added);
+
+ /* pages that are "onlined"/used from pages_added */
+ seq_printf(f, "%-22s: %u\n", "pages_onlined", dm->num_pages_onlined);
+
+ /* pages we have given back to host */
+ seq_printf(f, "%-22s: %u\n", "pages_ballooned", dm->num_pages_ballooned);
+
+ seq_printf(f, "%-22s: %lu\n", "total_pages_committed",
+ get_pages_committed(dm));
+
+ seq_printf(f, "%-22s: %llu\n", "max_dynamic_page_count",
+ dm->max_dynamic_page_count);
+
+ return 0;
+}
+
+DEFINE_SHOW_ATTRIBUTE(hv_balloon_debug);
+
+static void hv_balloon_debugfs_init(struct hv_dynmem_device *b)
+{
+ debugfs_create_file("hv-balloon", 0444, NULL, b,
+ &hv_balloon_debug_fops);
+}
+
+static void hv_balloon_debugfs_exit(struct hv_dynmem_device *b)
+{
+ debugfs_remove(debugfs_lookup("hv-balloon", NULL));
+}
+
+#else
+
+static inline void hv_balloon_debugfs_init(struct hv_dynmem_device *b)
+{
+}
+
+static inline void hv_balloon_debugfs_exit(struct hv_dynmem_device *b)
+{
+}
+
+#endif /* CONFIG_DEBUG_FS */
+
static int balloon_probe(struct hv_device *dev,
const struct hv_vmbus_device_id *dev_id)
{
@@ -1670,8 +1823,8 @@ static int balloon_probe(struct hv_device *dev,
cap_msg.hdr.size = sizeof(struct dm_capabilities);
cap_msg.hdr.trans_id = atomic_inc_return(&trans_id);
- cap_msg.caps.cap_bits.balloon = 1;
- cap_msg.caps.cap_bits.hot_add = 1;
+ cap_msg.caps.cap_bits.balloon = ballooning_enabled();
+ cap_msg.caps.cap_bits.hot_add = hot_add_enabled();
/*
* Specify our alignment requirements as it relates
@@ -1712,6 +1865,8 @@ static int balloon_probe(struct hv_device *dev,
dm_device.state = DM_INITIALIZED;
last_post_time = jiffies;
+ hv_balloon_debugfs_init(&dm_device);
+
return 0;
probe_error2:
@@ -1737,6 +1892,8 @@ static int balloon_remove(struct hv_device *dev)
if (dm->num_pages_ballooned != 0)
pr_warn("Ballooned pages: %d\n", dm->num_pages_ballooned);
+ hv_balloon_debugfs_exit(dm);
+
cancel_work_sync(&dm->balloon_wrk.wrk);
cancel_work_sync(&dm->ha_wrk.wrk);
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