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避免在价值可能相同时写字
原标题:Is it faster to avoid writes when the values might be the same
  • 时间:2012-05-19 04:20:44
  •  标签:
  • c
  • memory
  • smp

在SMP机器中,有2至1级的性能效益:

(1) x = 0;

2) if (x) x = 0;

我认为,在幕后,花钱管理各中心之间的切合。 Am子吗?

最佳回答

即便有单一读写的代码,如果标的在于复印时的记忆(例如,档案的私人测绘,或者在 for后几乎可以传承)。 我怀疑你再次提出的好处也是真实的,至少是在X86等系统,即自动处理记忆一致性问题。 在这种机器上,写上可能位于另一条交汇处的记忆,将使卡路里的复印件(实际上整个海滩线)失效。 仅读就没有受到伤害。 当然,如果这记忆有可能被多个线索改变和分享,那么它就需要通过同步机制加以保护,从而可能失去大多数或全部优势。

问题回答

It has to manage the cache coherency even if you are reading, so I don t think it s going to buy you anything. And it also is going to largely depend on what the compiler does. If you really care, I would benchmark it on the system you are using.





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