linux-kernel - Re: [PATCH 0/7] [RFC] kernel: add a netlink interface to get information about processes

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Message-ID: <20150227204346.GB28401@kernel.org>
Date:	Fri, 27 Feb 2015 17:43:46 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Pavel Odintsov <pavel.odintsov@...il.com>
Cc:	linux-kernel@...r.kernel.org, David Ahern <dsahern@...il.com>
Subject: Re: [PATCH 0/7] [RFC] kernel: add a netlink interface to get
 information about processes

Em Thu, Feb 19, 2015 at 05:00:12PM +0400, Pavel Odintsov escreveu:
> Hello!
> 
> In addition to my post I want to mention another issue related with
> slow /proc read in perf toolkit. On my server with 25 000 processes I
> need about ~15 minutes for loading perf top toolkit completely.
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=86991

Right, one way would be to, in the 'perf top' case to defer getting
thread information to when we need it, i.e. when we get a sample for a
pid that we have no struct thread associated with.

We would speed up 'perf top' startup but would introduce jitter down the
line, and would be up for races, but hey, we already are, using /proc
:-/

But that would not work for 'perf record', as we need to in advance
generate those records as we don't do any processing of samples...

Yeah, for preexisting threads we do have a problem since day one, what
we use is just what can be done with existing stuff.

I saw that there were some more messages in this thread, its just that I
haven't found them in my mailbox when David Ahern pointed this out this
discussion to me :-\

>From the subject line, there is patchkit, but I couldn't find it... Can
you resend it to me or point me to some url where I can get it?

- Arnaldo
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