high memory usage

Hi all,

I have a Windows 2008 R2 box running SQL 2008 R2 64 bit.

I have 44 Gigs of RAM installed on my server..I have installed SQL server 2008r2 with 5 instance(One default+4 named instances) and SQL is using 43.8 Gigs of the RAM according to Task Manager.

Is this normal? if not  please provide solution for reducing memory usage.

Thank you,

Raj