Re: [PATCH 3/3] perf record: mmap output file

[David Ahern]

On 10/15/13 9:27 AM, Ingo Molnar wrote:
> * Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> > On Tue, Oct 15, 2013 at 11:32:45AM -0300, Arnaldo Carvalho de Melo wrote:
> >
> > > Jiri and PeterZ probaby will have comments here... ;-) :-)
> >
> > The only complication with splice is the vmalloc support; other than
> > that it should be fairly straight fwd.
>
> In the initial version we could skip splice support for vmalloc
> ring-buffer, to keep things simple.
>
> Wanna send a patch for people to try? Looks like there's real interest in
> speeding up perf record as much as possible!

My second -- and more important -- concern about splice has been dropped 
from this path:

"splice is also a system call and it would have to be invoked for each 
mmap each trip through the loop -- just like write() does today -- so it 
does not solve the feedback loop problem. "

Am I missing something on how splice works?

David

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/