Question about memcpy

[bing zhu]

Thanks for elaborating ,I've learned that it's not worth it,i'm turning
other ways for performance consideration ,thanks!

2018-07-13 15:33 GMT+08:00 <valdis.kletnieks at vt.edu>:

> On Fri, 13 Jul 2018 11:02:13 +0800, bing zhu said:
>
> > I‘m trying to write a simple fs in user space,if memcpy is slower than
> > kernel , i think it's unfair,as for only cpu for my task,
> > it's a bit of arbitrary ，i just want my task not interrupted during a
> > specific time is that possible ?
>
> Not getting interrupted is an *entirely* different issue than making
> memcpy fast.
>
> Note that in general, systems code should be able to deal with
> interruptions
> during most parts of the code, and locking used and disabling pre-emption
> for
> sections of code that can't deal with being interrupted.  Remember that if
> your
> filesystem code turns off interrupts for long enough, you can start losing
> things like I/O completions.  Fortunately for those who write systems code,
> the vast majority of interrupts are totally transparent to the vast
> majority
> of the kernel code.
>
> And if you're doing a file system in userspace, you're going to fail to
> notice
> hundreds or even thousands of interrupts happening. If you don't believe
> me,
> 'cat /proc/interrupts', and realize that userspace didn't notice *any* of
> them
> happening.
>
>
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