cpu-cache

I am interested in forcing a CPU cache flush in Windows (for benchmarking reasons, I want to emulate starting with no data in CPU cache), preferably a basic C implementation or Win32 call. Is there a known way to do this with a system call or even something as sneaky as doing say a large memcpy ? Intel i686 platform (P4 and up is okay as well). Gunther Piez Fortunately, there is more than one way to explicitly flush the caches. The instruction "wbinvd" writes back modified cache content and marks the caches empty. It executes a bus cycle to make external caches flush their data. Unfortunately,

I am trying to use clflush to manually evicts a cache line in order to determine cache and line sizes. I didn't find any guide on how to use that instruction. All I see, are some codes that use higher level functions for that purpose. There is a kernel function void clflush_cache_range(void *vaddr, unsigned int size) , but still I don't know what to include in my code and how to use that. I don't know what is the size in that function. More than that, how can I be sure that the line is evicted in order to verify the correctness of my code? UPDATE: Here is a initial code for what I am trying to

When executing a series of _mm_stream_load_si128() calls ( MOVNTDQA ) from consecutive memory locations, will the hardware pre-fetcher still kick-in, or should I use explicit software prefetching (with NTA hint) in order to obtain the benefits of prefetching while still avoiding cache pollution? The reason I ask this is because their objectives seem contradictory to me. A streaming load will fetch data bypassing the cache, while the pre-fetcher attempts to proactively fetch data into the cache. When sequentially iterating a large data structure (processed data won't be retouched in a long

This question already has an answer here: Why does the order of the loops affect performance when iterating over a 2D array? 7 answers Which of the following orderings of nested loops to iterate over a 2D array is more efficient in terms of time (cache performance)? Why? int a[100][100]; for(i=0; i<100; i++) { for(j=0; j<100; j++) { a[i][j] = 10; } } or for(i=0; i<100; i++) { for(j=0; j<100; j++) { a[j][i] = 10; } } The first method is slightly better, as the cells being assigned to lays next to each other. First method: [ ][ ][ ][ ][ ] .... ^1st assignment ^2nd assignment [ ][ ][ ][ ][ ] ....

I have learned about different cache mapping technique like direct mapping,associate mapping and set associative mapping technique and also learned the trade-offs. But I am curious what is used in intel core i7 or AMD processor nowadays. And how the techniques are evolved. And what are things that needs to be improved? Direct-mapped caches are basically never used in modern high-performance CPUs . The power savings are outweighed by the large advantage in hit rate for a set-associative cache of the same size, with only a bit more complexity in the control logic. Transistor budgets are very

Why is the size of L1 cache smaller than that of the L2 cache in most of the processors ? There are different reasons for that. L2 exists in the system to speedup the case where there is a L1 cache miss. If the size of L1 was the same or bigger than the size of L2, then L2 could not accomodate for more cache lines than L1, and would not be able to deal with L1 cache misses. From the design/cost perspective, L1 cache is bound to the processor and faster than L2. The whole idea of caches is that you speed up access to the slower hardware by adding intermediate hardware that is more performing