tlb | 易学教程

cache miss, a TLB miss and page fault

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问题 Can someone clearly explain me the difference between a cache miss, a tlb miss and page fault, and how do these affect the effective memory access time? 回答1: Let me explain all these things step by step. The CPU generates the logical address, which contains the page number and the page offset . The page number is used to index into the page table , to get the corresponding page frame number , and once we have the page frame of the physical memory (also called main memory), we can apply the

Difference between logical addresses, and physical addresses?

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问题 I am reading Operating Systems Concept and I am on the 8th chapter! However I could use some clarification, or reassurance that my understanding is correct. Logical Addresses: Logical addresses are generated by the CPU, according to the book. What exactly does this mean? (In an execute-generated address system..) I assume when code is compiled for a program, the program has no idea where the code will be loaded in memory. All the compiler does is set up a general sketch of the program layout

In what circumstances can large pages produce a speedup?

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问题 Modern x86 CPUs have the ability to support larger page sizes than the legacy 4K (ie 2MB or 4MB), and there are OS facilities (Linux, Windows) to access this functionality. The Microsoft link above states large pages "increase the efficiency of the translation buffer, which can increase performance for frequently accessed memory". Which isn't very helpful in predicting whether large pages will improve any given situation. I'm interested in concrete, preferably quantified, examples of where

how to interpret perf iTLB-loads,iTLB-load-misses

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问题 I have a test case to observe perf iTLB-loads,iTLB-load-misses by perf stat -e dTLB-loads,dTLB-load-misses,iTLB-loads,iTLB-load-misses -p 22479 and get the output : Performance counter stats for process id '22479': 1,262,817 dTLB-loads 13,950 dTLB-load-misses # 1.10% of all dTLB cache hits 75 iTLB-loads 6,882 iTLB-load-misses # 9176.00% of all iTLB cache hits 3.999720948 seconds time elapsed I have no idea how to interpret iTLB-loads only 75 but iTLB-load-misses 6,882 ?! lscpu showes : Intel

What happens after a L2 TLB miss?

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I'm struggling to understand what happens when the first two levels of the Translation Lookaside Buffer result in misses? I am unsure whether "page walking" occurs in special hardware circuitry, or whether the page tables are stored in the L2/L3 cache, or whether they only reside in main memory. Modern x86 microarchitectures have dedicated page-walk hardware . They can even speculatively do page-walks to load TLB entries before a TLB miss actually happens . Skylake can even have two page walks in flight at once, see Section 2.1.3 of Intel's optimization manual . This may be related to the page

What happens after a L2 TLB miss?

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问题 I\'m struggling to understand what happens when the first two levels of the Translation Lookaside Buffer result in misses? I am unsure whether \"page walking\" occurs in special hardware circuitry, or whether the page tables are stored in the L2/L3 cache, or whether they only reside in main memory. 回答1: (Some of this is x86 and Intel-specific. Most of the key points apply to any CPU that does hardware page walks. I also discuss ISAs like MIPS that handle TLB misses with software.) Modern x86