The high precision of the latest version of the planetary ephemeris EPM2011 enables one to explore more accurately a variety of small effects in the solar system. The processing of about 678 thousand of position observations of planets and spacecrafts for 1913--2011 with the predominance of modern radar measurements resulted in improving the PPN parameters, dynamic oblateness of the Sun, secular variation of the heliocentric gravitational constant $GM_{\odot}$, and variation range of the gravitational constant $G$. This processing made it possible to estimate the potential additional gravitational influence of dark matter on the motion of the solar system bodies. The density of dark matter ${\rho}_{dm}$, if any, turned out to be substantially below the accuracy achieved by the present determination of such parameters. At the distance of the orbit of Saturn the density ${\rho}_{dm}$ is estimated to be under $1.1\cdot10^{-20}$ g/cm$^3$, and the mass of dark matter in the area inside the orbit of Saturn is less than $7.9\cdot10^{-11}$ M$_{\odot}$ even taking into account its possible tendency to concentrate in the center.