\definecolor{mygreen}{HTML}{129d1c}
\pgfplotsset{scaled y ticks=false,scaled x ticks=false}
\begin{tikzpicture}
  \begin{axis}[
      xlabel=$Nombre\ de\ sources$,%0 -> 250 000
      ylabel=$Temps\ moyen\ (en\ ms)$, %0 -> 1 600 000
      %ylabel style={xshift=-5pt,yshift=15pt},
      ylabel style={yshift=20pt},
      legend cell align=left,
      legend style={draw=none,legend pos=north west,font=\small},
      xticklabel style={/pgf/number format/fixed},
      yticklabel style={/pgf/number format/fixed},
%      ytick={aaa,1000000,1500000},
     /pgf/number format/1000 sep={\ }]

     \addplot[color=mygreen,mark=+] plot coordinates {
%      (4,      )
      (20,     16.7)
      (200,    66)
      (1000,   208.6)
      (2000,   359.6)
      (4000,   833.4)
      (6000,   1470)
      (8000,   2409.4)
      (10000,  3610.2)
      (20000,  13436.8)
      (40000,  52300.5)
      (100000, 322164.1)
      (200000, 1250304.9)
%      (2000000, 131216793.1)
    } ;
    %} node[pos=0.8,pin={$P_1$},xshift=0.5cm,yshift=-0.5cm] {} ;
    %} node[pos=0.1,pin=135:{\color{purple}$A$}] {} ;
    %node[pos=0.54](endofplotsquare){} ;
    %\node [right, color=mygreen] at (endofplotsquare) {A};
    %\node at (200000,300000) {\color{mygreen}$P_1$};
    \node at (210,125) {\color{mygreen}$P_1$};
    \addlegendentry{({\color{mygreen}$P_1$}) Temps moyen phase \#1}

    \addplot[color=blue,mark=+] plot coordinates {
%      (4,      )
      (20,     0.5)
      (200,    6.8)
      (1000,   28.7)
      (2000,   54)
      (4000,   142.7)
      (6000,   223.8)
      (8000,   342.4)
      (10000,  491.4)
      (20000,  1760)
      (40000,  6781.2)
      (100000, 41708.1)
      (200000, 166934.2)
%      (2000000, 2338520.8)
    } ;
    %} node[pos=1,pin={$P_2$}] {} ;
    \node at (210,17) {\color{blue}$P_2$};
    %\node[pin=Toto $P_2$] at (axis cs:200000,300000) {};
    \addlegendentry{({\color{blue}$P_2$}) Temps moyen phase \#2}

    \addplot[color=red,mark=+] plot coordinates {
%      (4,      )
      (20,     17.2)
      (200,    72.8)
      (1000,   237.3)
      (2000,   413.6)
      (4000,   976.1)
      (6000,   1693.8)
      (8000,   2751.8)
      (10000,  4101.6)
      (20000,  15196.8)
      (40000,  59081.7)
      (100000, 363872.2)
      (200000, 1417239.1)
 %     (2000000, 154602033.9)
  } ;
  %} node[pos=0.9,pin={$T$}] {} ;
    \node at (210,142) {\color{myred}$T$};
    \addlegendentry{({\color{myred}$T$})~ Temps moyen total}

    %\legend{$d=2$\\$d=3$\\$d=4$\\$d=5$\\$d=6$\\}
  \end{axis}
\end{tikzpicture}