我的应用程序中有一堆缓冲区(其中25到30个)相当大(.5mb)并且访问了simulataneousley.更糟糕的是,它们中的数据通常只读取一次,并且经常更新(例如每秒30次).排序非理想缓存使用的完美风暴.
无论如何,我想到如果我能将一块内存标记为不可缓存的话会很酷……从理论上讲,这将为缓存中的其他所有内容留出更多空间.
那么,他们是一种在Linux中标记为不可缓存的内存块的方法吗？
如何避免使用这样的数据来污染缓存
What Every Programmer Should Know About Memory(PDF) – 这是从红帽开发的角度编写的,非常适合您.但是,大部分都是跨平台的.
您想要的是“非时间访问”,并告诉处理器期望您现在正在阅读的值暂时不再需要.然后处理器避免缓存该值.
请参阅上面链接的PDF的第49页.它使用intel内在函数在缓存周围进行流式处理.
On the read side,processors,until
recently,lacked support aside from
weak hints using non-temporal access
(NTA) prefetch instructions. There is
no equivalent to write-combining for
reads,which is especially bad for
uncacheable memory such as
memory-mapped I/O. Intel,with the
SSE4.1 extensions,introduced NTA
loads. They are implemented using a
small number of streaming load
buffers; each buffer contains a cache
line. The first movntdqa instruction
for a given cache line will load a
cache line into a buffer,possibly
replacing another cache line.
Subsequent 16-byte aligned accesses to
the same cache line will be serviced
from the load buffer at little cost.
Unless there are other reasons to do
so,the cache line will not be loaded
into a cache,thus enabling the
loading of large amounts of memory
without polluting the caches. The
compiler provides an intrinsic for
this instruction:
#include <smmintrin.h>
__m128i _mm_stream_load_si128 (__m128i *p);
This intrinsic should be used multiple times,with addresses of
16-byte blocks passed as the
parameter,until each cache line is
read. Only then should the next cache
line be started. Since there are a few
streaming read buffers it might be
possible to read from two memory
locations at once
如果在读取时,缓冲区通过内存以线性顺序读取,那将是完美的.您使用流式读取来执行此操作.当您想要修改它们时,缓冲区将按线性顺序进行修改,如果您不希望在同一个线程中很快再次读取它们,则可以使用流式写入来执行此操作.
