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[Xen-devel] [PATCH 3/7] xl: 'xl info' print outstanding claims if enabled (claim_mode=1 in xl.conf)

This patch provides the value of the currently outstanding pages
claimed for all domains. This is a total global value that influences
the hypervisors' MM system.

When a claim call is done, a reservation for a specific amount of pages
is set and also a global value is incremented. This global value is then
reduced as the domain's memory is populated and eventually reaches zero.
The toolstack (libxc) also sets the domain's claim to zero when the population
of memory has completed as an extra step. Any call to destroy the domain
will also set the domain's claim to zero.

If the reservation cannot be meet the guest creation fails immediately
instead of taking seconds or minutes (depending on the size of the guest)
while the toolstack populates memory.

See patch: "xl: Implement XENMEM_claim_pages support via 'claim_mode'
global config" for details on how it is implemented.

The value fluctuates quite often so the value is stale once it is provided
to the user-space.  However it is useful for diagnostic purposes.

It is only printed when the global "claim_mode" option in xl.conf(5)
is set to enabled (1). The 'man xl' shows the details of this item.

[v1: s/unclaimed/outstanding/]
[v2: Made libxl_get_claiminfo return just MemKB suggested by Ian Campbell]
[v3: Made libxl_get_claininfo return MemMB to conform to the other values 
[v4: Improvements suggested by Ian Jackson, also added docs to xl.pod.1]
[v5: Clarify how claims are cancelled, split >72 characters - Ian Jackson]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
 docs/man/xl.pod.1        | 10 ++++++++++
 tools/libxl/libxl.c      | 14 ++++++++++++++
 tools/libxl/libxl.h      |  1 +
 tools/libxl/xl_cmdimpl.c | 24 ++++++++++++++++++++++++
 4 files changed, 49 insertions(+)

diff --git a/docs/man/xl.pod.1 b/docs/man/xl.pod.1
index a0e298e..d8783e8 100644
--- a/docs/man/xl.pod.1
+++ b/docs/man/xl.pod.1
@@ -704,6 +704,7 @@ Sample output looks as follows:
  total_memory           : 6141
  free_memory            : 4274
  free_cpus              : 0
+ outstanding_claims     : 0
  xen_major              : 4
  xen_minor              : 2
  xen_extra              : -unstable
@@ -738,6 +739,15 @@ the feature bits returned by the cpuid command on x86 
 Available memory (in MB) not allocated to Xen, or any other domains.
+=item B<outstanding_claims>
+When a claim call is done (see L<xl.conf>) a reservation for a specific
+amount of pages is set and also a global value is incremented. This
+global value (outstanding_claims) is then reduced as the domain's memory
+is populated and eventually reaches zero. Most of the time the value will
+be zero, but if you are launching multiple guests, and B<claim_mode> is
+enabled, this value can increase/decrease.
 =item B<xen_caps>
 The Xen version and architecture.  Architecture values can be one of:
diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 572c2c6..230b954 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -4057,6 +4057,20 @@ libxl_numainfo *libxl_get_numainfo(libxl_ctx *ctx, int 
     return ret;
+uint64_t libxl_get_claiminfo(libxl_ctx *ctx)
+    long l;
+    l = xc_domain_get_outstanding_pages(ctx->xch);
+    if (l < 0) {
+                            "xc_domain_get_outstanding_pages failed.");
+        return ERROR_FAIL;
+    }
+    /* In MB */
+    return (l >> 8);
 const libxl_version_info* libxl_get_version_info(libxl_ctx *ctx)
     union {
diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index e4a4ab2..4922313 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -595,6 +595,7 @@ int libxl_wait_for_free_memory(libxl_ctx *ctx, uint32_t 
domid, uint32_t memory_k
 /* wait for the memory target of a domain to be reached */
 int libxl_wait_for_memory_target(libxl_ctx *ctx, uint32_t domid, int 
+uint64_t libxl_get_claiminfo(libxl_ctx *ctx);
 int libxl_vncviewer_exec(libxl_ctx *ctx, uint32_t domid, int autopass);
 int libxl_console_exec(libxl_ctx *ctx, uint32_t domid, int cons_num, 
libxl_console_type type);
 /* libxl_primary_console_exec finds the domid and console number
diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
index 5a0506f..c9b71e6 100644
--- a/tools/libxl/xl_cmdimpl.c
+++ b/tools/libxl/xl_cmdimpl.c
@@ -4666,6 +4666,29 @@ static void output_topologyinfo(void)
+static void output_claim(void)
+    long l;
+    /*
+     * Note that the xl.c (which calls us) has already read from the
+     * global configuration the 'claim_mode' value.
+     */
+    if (!libxl_defbool_val(claim_mode))
+        return;
+    l = libxl_get_claiminfo(ctx);
+    if (l < 0) {
+        fprintf(stderr, "libxl_get_claiminfo failed. errno: %d (%s)\n",
+                errno, strerror(errno));
+        return;
+    }
+    printf("outstanding_claims     : %ld\n", l);
+    return;
 static void print_info(int numa)
@@ -4676,6 +4699,7 @@ static void print_info(int numa)
+    output_claim();

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