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Bulk operations work better than large number of

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Unformatted text preview: sing a cost benefit policy Systems Systems Mantras Be clever at high utilization! Bulk operations work better than large number of smaller ones Indirection, indirection, …. LFS LFS Improves performance significantly for writes to small files - influenced journalling Cute idea but … never put in production file systems compatibility issues with existing FSs reads may be slower (for fragmented files) – cache is never big enough read bandwidth may be poor for large files -> want contiguity latency improvements are on the horizon - SSDs, PCM, RamCloud (Stanford) Break Break CSci CSci 5103 Operating Systems Protection Chap 9 Protection Protection What are we protecting? files, CPU, memory, peripherals, etc Think of these as objects Rights: what can be done to w/r an object Domain: object, rights pairs Subject: “who or what” is doing the accessing Protection Domains How are domains established and by whom? A process runs in a domain – set of objects it can access Protection Domains A protection matrix: maintained in the OS Protection Domains A protection matrix with domains as objects How this can be done in Unix? Access Control Lists Vertical slice of matrix Capabilities Horizontal slice of matrix When capabilities are used, each process has a capability list In kernel -> Hydra OS Capabilities check known to server Client held capabilities – if in possession of one, have its rights Extends nicely to distributed systems A cryptographically protected capability – why? What doesn’t this protect against? Capabilities Object specific rights: read, append, draw...
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