Use @bigmemtest more accurately.

diff --cc Lib/test/test_strtod.py
index eee8a23228462e7f35aca1920c31562bfd464724,c5979fc98995fe544b88e250c9a061a57faabe09..41b6e5f8332dbdcdbf3debe17aa81c1956044f45
--- 1/Lib/test/test_strtod.py
--- 2/Lib/test/test_strtod.py
+++ b/Lib/test/test_strtod.py
@@@ -248,10 -248,10 +248,10 @@@ class StrtodTests(unittest.TestCase)
                      else:
                          assert False, "expected ValueError"
  
-     @test.support.bigmemtest(size=5 * test.support._1G, memuse=1, dry_run=False)
 -    @test.support.bigmemtest(size=test.support._2G+10, memuse=4, dry_run=False)
++    @test.support.bigmemtest(size=test.support._2G+10, memuse=3, dry_run=False)
      def test_oversized_digit_strings(self, maxsize):
          # Input string whose length doesn't fit in an INT.
-         s = "1." + "1" * int(2.2e9)
+         s = "1." + "1" * maxsize
          with self.assertRaises(ValueError):
              float(s)
          del s