segmap_percent adjusts the percentage of memory that the kernel maps into its address space for the file system cache. The default value is 12, that is, the kernel reserves enough space to map at most 12% of memory for the file system cache. On a heavily loaded machine with 4 Gbytes of physical memory, improvements have been seen with values as high as 60. You can experiment with this value, starting with values around 25. On systems with large amounts of physical memory, you can raise this value in small increments, as it can significantly increase kernel memory requirements.