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sendmail Performance Tuning by Nick Christenson

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7.1. Kernel Parameters Run Amok

Let’s consider a real-life example. The Solaris operating system from Sun Microsystems contains a kernel table called the Directory Name Lookup Cache (DNLC). The DNLC is a kernel cache that matches the name of a recently accessed file with its vnode (a virtual inode, an extra level of abstraction that makes writing interfaces to filesystems easier and more portable) if the file name isn’t too long. Keeping this table in memory means that if a file is opened once by a process, and then opened again within a short period of time, the second open() won’t require a directory lookup to retrieve the file’s inode. If many of the open()s performed by the system operate on the same files over and over, this strategy could ...

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