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From: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
To: Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Tim Murray <timmurray-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
	Sonny Rao <sonnyrao-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
	Daniel Colascione
	<dancol-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
	Minchan Kim <minchan-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Joel Fernandes <joelaf-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
	Al Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Linux-MM <linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org>,
	Robert Foss <robert.foss-ZGY8ohtN/8qB+jHODAdFcQ@public.gmane.org>,
	linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Luigi Semenzato
	<semenzato-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Subject: Re: [PATCH RFC v2] Add /proc/pid/smaps_rollup
Date: Fri, 25 Aug 2017 14:16:37 -0700	[thread overview]
Message-ID: <20170825141637.f11a36a9997b4b705d5b6481@linux-foundation.org> (raw)
In-Reply-To: <20170824085553.GB5943-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>

On Thu, 24 Aug 2017 10:55:53 +0200 Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> wrote:

> > If we assume that the number of VMAs is going to increase over time,
> > then doing anything we can do to reduce the overhead of each VMA
> > during PSS collection seems like the right way to go, and that means
> > outputting an aggregate statistic (to avoid whatever overhead there is
> > per line in writing smaps and in reading each line from userspace).
> > 
> > Also, Dan sent me some numbers from his benchmark measuring PSS on
> > system_server (the big Android process) using smaps vs smaps_rollup:
> > 
> > using smaps:
> > iterations:1000 pid:1163 pss:220023808
> >  0m29.46s real 0m08.28s user 0m20.98s system
> > 
> > using smaps_rollup:
> > iterations:1000 pid:1163 pss:220702720
> >  0m04.39s real 0m00.03s user 0m04.31s system
> 
> I would assume we would do all we can to reduce this kernel->user
> overhead first before considering a new user visible file. I haven't
> seen any attempts except from the low hanging fruid I have tried.

It's hard to believe that we'll get anything like a 5x speedup via
optimization of the existing code?

  parent reply	other threads:[~2017-08-25 21:16 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20170808132554.141143-1-dancol@google.com>
     [not found] ` <20170810001557.147285-1-dancol@google.com>
     [not found]   ` <20170810043831.GB2249@bbox>
2017-08-10  8:46     ` [PATCH RFC v2] Add /proc/pid/smaps_rollup Michal Hocko
2017-08-10 10:23       ` Daniel Colascione
2017-08-10 10:58         ` Michal Hocko
     [not found]           ` <20170810105852.GM23863-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2017-08-10 18:56             ` Sonny Rao
2017-08-10 19:17               ` Tim Murray
2017-08-24  8:55                 ` Michal Hocko
     [not found]                   ` <20170824085553.GB5943-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2017-08-25 21:16                     ` Andrew Morton [this message]
     [not found]                       ` <20170825141637.f11a36a9997b4b705d5b6481-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
2017-08-28 11:30                         ` Michal Hocko

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