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RE: Patch to eliminate user space memory copying in 'cp'
From: |
Spinka, Kristofer |
Subject: |
RE: Patch to eliminate user space memory copying in 'cp' |
Date: |
Sat, 5 Apr 2003 19:13:25 -0500 |
I agree that there wasn't any notable "copy" I/O performance increase,
but the CPU cycles and memory I/O are significantly reduced.
So while most modern machines' have CPUs and memory buses that have
plenty of room for inefficient user-space copies on a quiescent machine,
it's the efficiency I was looking for. I think on a heavily loaded
machine or with a serious disk subsystem the difference would be more
apparent to the user.
/kristofer
> -----Original Message-----
> From: Jim Meyering [mailto:address@hidden
> Sent: Saturday, April 05, 2003 1:29 PM
> To: Spinka, Kristofer
> Cc: address@hidden
> Subject: Re: Patch to eliminate user space memory copying in 'cp'
>
> Jim Meyering <address@hidden> wrote:
> > "Spinka, Kristofer" <address@hidden> wrote:
> >> You will have to incorporate the check for sendfile, but
otherwise
> >> this patch should avoid the most common kernel<->user space
read/write
> >> transitions.
> >
> > Thank you for that patch. It looks like a fine optimization.
> >
> > I'll work on integrating it after coreutils-5.0.
>
> After a few simple tests, I don't see any performance
> benefit to using sendfile. Do you have evidence that
> using sendfile is worthwhile?