[PULL,20/49] scripts/kvm/kvm_stat: Set sensible no. files rlimit

Commit Message

Paolo Bonzini Jan. 26, 2016, 1:46 p.m. UTC

From: Janosch Frank <[e-mail]>

As num cpus * 1000 is NOT a sensible rlimit, we need to calculate a
more accurate rlimit.

The number of open files is directly dependent on the cpu count and on
the number of trace points per cpu. A additional constant works as a
buffer for files that are needed by python or do get opened when the
script runs.

Hence we have:
      cpus * traces + constant

Reviewed-by: Jason J. Herne <[e-mail]>
Signed-off-by: Janosch Frank <[e-mail]>
Message-Id: <[e-mail]>
Signed-off-by: Paolo Bonzini <[e-mail]>
---
 scripts/kvm/kvm_stat | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

Patch

diff --git a/scripts/kvm/kvm_stat b/scripts/kvm/kvm_stat
index 457624d..93b5ea7 100755
--- a/scripts/kvm/kvm_stat
+++ b/scripts/kvm/kvm_stat
@@ -395,8 +395,15 @@  class TracepointProvider(object):
     def _setup(self, _fields):
         self._fields = _fields
         cpus = self._online_cpus()
-        nfiles = len(cpus) * 1000
-        resource.setrlimit(resource.RLIMIT_NOFILE, (nfiles, nfiles))
+
+        # The constant is needed as a buffer for python libs, std
+        # streams and other files that the script opens.
+        rlimit = len(cpus) * len(_fields) + 50
+        try:
+            resource.setrlimit(resource.RLIMIT_NOFILE, (rlimit, rlimit))
+        except ValueError:
+            sys.exit("NOFILE rlimit could not be raised to {0}".format(rlimit))
+
         events = []
         self.group_leaders = []
         for cpu in cpus: