tomcat启动参数调优

　　-XX:PrintHeapAtGC:打印GC前后的详细堆栈信息
　　输出形式：
　　34.702: [GC {Heap before gc invocations=7:
　　def new generation  total 55296K, used 52568K [0x1ebd0000, 0x227d0000, 0x227d0000)
　　eden space 49152K, 99% used [0x1ebd0000, 0x21bce430, 0x21bd0000)
　　from space 6144K, 55% used [0x221d0000, 0x22527e10, 0x227d0000)
　　to  space 6144K,  0% used [0x21bd0000, 0x21bd0000, 0x221d0000)
　　tenured generation  total 69632K, used 2696K [0x227d0000, 0x26bd0000, 0x26bd0000)
　　the space 69632K,  3% used [0x227d0000, 0x22a720f8, 0x22a72200, 0x26bd0000)
　　compacting perm gen total 8192K, used 2898K [0x26bd0000, 0x273d0000, 0x2abd0000)
　　the space 8192K, 35% used [0x26bd0000, 0x26ea4ba8, 0x26ea4c00, 0x273d0000)
　　ro space 8192K, 66% used [0x2abd0000, 0x2b12bcc0, 0x2b12be00, 0x2b3d0000)
　　rw space 12288K, 46% used [0x2b3d0000, 0x2b972060, 0x2b972200, 0x2bfd0000)
　　34.735: [DefNew: 52568K->3433K(55296K), 0.0072126 secs] 55264K->6615K(124928K)Heap after gc invocations=8:
　　def new generation  total 55296K, used 3433K [0x1ebd0000, 0x227d0000, 0x227d0000)
　　eden space 49152K,  0% used [0x1ebd0000, 0x1ebd0000, 0x21bd0000)
　　from space 6144K, 55% used [0x21bd0000, 0x21f2a5e8, 0x221d0000)
　　to  space 6144K,  0% used [0x221d0000, 0x221d0000, 0x227d0000)
　　tenured generation  total 69632K, used 3182K [0x227d0000, 0x26bd0000, 0x26bd0000)
　　the space 69632K,  4% used [0x227d0000, 0x22aeb958, 0x22aeba00, 0x26bd0000)
　　compacting perm gen total 8192K, used 2898K [0x26bd0000, 0x273d0000, 0x2abd0000)
　　the space 8192K, 35% used [0x26bd0000, 0x26ea4ba8, 0x26ea4c00, 0x273d0000)
　　ro space 8192K, 66% used [0x2abd0000, 0x2b12bcc0, 0x2b12be00, 0x2b3d0000)
　　rw space 12288K, 46% used [0x2b3d0000, 0x2b972060, 0x2b972200, 0x2bfd0000)
　　}
　　, 0.0757599 secs]