Re: [PATCH 3/3] perf record: mmap output file
From: Arnaldo Carvalho de Melo
Date: Tue Oct 15 2013 - 10:33:01 EST
Em Tue, Oct 15, 2013 at 08:04:15AM -0600, David Ahern escreveu:
> On 10/8/13 11:59 PM, Ingo Molnar wrote:
> > 2)
> > Yet another method would be to avoid the copies altogether via the splice
> > system-call - see:
> > git grep splice kernel/trace/
> > To make splice low-overhead we'd have to introduce a mode to not mmap
> > the data part of the perf ring-buffer and splice the data straight
> > from the perf fd into a temporary pipe and over from the pipe into
> > the target file (or socket).
> I looked into splice and it was not clear it would be a good match.
> First, perf is setup to pull data from mmap's and there is not a 1:1
> association between mmap's and fd's (fd_in for splice). Second and
Jiri and PeterZ probaby will have comments here... ;-) :-)
Jiri even have patches, IIRC.
- Arnaldo
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