On Mon, Sep 09, 2013 at 01:17:49PM +0200, Peter Zijlstra wrote:
> On Sun, Sep 01, 2013 at 12:36:11PM +0200, Jiri Olsa wrote:
> > hi,
> > sending the support for multiple file storage. Initial
> > RFC is here:
> > http://marc.info/?l=linux-kernel&m=137408381902423&w=2
> >
> > v2 changes:
> > - reworked perf mmap size setup to be able to get
> > the mmap size value easily later
> > - added perf.data read/write test for v2 and v3
> > for both endianity
> > - added record '-M time' support
>
> So this 0/n post seems to have forgotten to list the rationale for doing
> all this..
here it is:
This patchset is actually doing 3 essential things:
1) adds new perf data format version (v3)
2) adds class/object to handle perf data file
3) adds record '-M size' option
ad 1) Along the way I realized it'd be much easier to have the
format simplified. I ended up with just 'DATA' and 'FEATURES'
sections making the file format more generic.
The easier/generic format will be for example useful for the
cpu hotplug notification (and maybe even for ftrace data files
features?)
The version 2 should be still readable by perf, while it
produces data in version 3 from this patchset onwards.
ad 2) I needed to unify perf data file handling to make the -M
implementation clear.
>
> The only reason I wanted this is so that each thread can write its own
> data. The current one file thing is an immense bottle-neck for big
> machines.
>
I haven't considered the thread based storage yet, but I
think having the simplified format and centralized file
handling will only help.
jirka
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