tlb

I can't understand the answer to this question: Consider an OS using one level of paging with TLB registers. If the page fault rate is 10% and dirty pages should be reloaded when needed, calculate the effective access time if: TLB Lookup = 20 ns TLB Hit ratio = 80% Memory access time = 75 ns Swap page time = 500,000 ns 50% of pages are dirty. Answer: T = 0.8(TLB+MEM) + 0.2 ( 0.9[TLB+MEM+MEM] + 0.1[TLB+MEM + 0.5(Disk) + 0.5(2Disk+MEM)] ) = 15,110 ns Can you explain why? In this context "effective" time means "expected" or "average" time. So you take the times it takes to access the page in the

Prologue I am an operating system hobbyist, and my kernel runs on 80486+, and already supports virtual memory. Starting from 80386, the x86 processor family by Intel and various clones thereof has supported virtual memory with paging. It is well known that when the PG bit in CR0 is set, the processor uses virtual address translation. Then, the CR3 register points to the top-level page directory, that is the root for 2-4 levels of page table structures that map the virtual addresses to physical addresses. The processor does not consult these tables for each virtual address generated, instead

Memory barriers guarantee that the data cache will be consistent. However, does it guarantee that the TLB will be consistent? I am seeing a problem where the JVM (java 7 update 1) sometimes crashes with memory errors (SIGBUS, SIGSEG) when passing a MappedByteBuffer between threads. e.g. final AtomicReference<MappedByteBuffer> mbbQueue = new AtomicReference<>(); // in a background thread. MappedByteBuffer map = raf.map(MapMode.READ_WRITE, offset, allocationSize); Thread.yield(); while (!inQueue.compareAndSet(null, map)); // the main thread. (more than 10x faster than using map() in the same

Is it possible to get list of translations (from virtual pages into physical pages) from TLB (Translation lookaside buffer, this is a special cache in the CPU). I mean modern x86 or x86_64; and I want to do it in programmatic way, not by using JTAG and shifting all TLB entries out. The linux kernel has no such dumper, there is page from linux kernel about cache and tlb: https://www.kernel.org/doc/Documentation/cachetlb.txt "Cache and TLB Flushing Under Linux." David S. Miller There was an such TLB dump in 80386DX (and 80486, and possibly in "Embedded Pentium" 100-166 MHz / " Embedded Pentium

I've heard that TLB is maintained by the MMU not the CPU cache. Then Does One TLB exist on the CPU and is shared between all processor or each processor has its own TLB cache? Could anyone please explain relationship between MMU and L1, L2 Cache? The TLB caches the translations listed in the page table. Each CPU core can be running in a different context, with different page tables. This is what you'd call the MMU, if it was a separate "unit", so each core has its own MMU. Any shared caches are always physically-indexed / physically tagged, so they cache based on post-MMU physical address. The