From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Vlastimil Babka <vbabka@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Michal Nazarewicz <mina86@mina86.com>,
Minchan Kim <minchan@kernel.org>, Mel Gorman <mgorman@suse.de>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-api@vger.kernel.org
Subject: Re: [PATCH 2/2] mm/page_ref: add tracepoint to track down page reference manipulation
Date: Tue, 24 Nov 2015 10:45:28 +0900 [thread overview]
Message-ID: <20151124014527.GA32335@js1304-P5Q-DELUXE> (raw)
In-Reply-To: <20151123092604.7ec1397d@gandalf.local.home>
On Mon, Nov 23, 2015 at 09:26:04AM -0500, Steven Rostedt wrote:
> On Mon, 23 Nov 2015 17:28:05 +0900
> Joonsoo Kim <iamjoonsoo.kim@lge.com> wrote:
>
> > On Fri, Nov 20, 2015 at 11:42:25AM -0500, Steven Rostedt wrote:
> > > On Fri, 20 Nov 2015 15:33:25 +0900
> > > Joonsoo Kim <iamjoonsoo.kim@lge.com> wrote:
> > >
> > >
> > > > Steven, is it possible to add tracepoint to inlined fucntion such as
> > > > get_page() in include/linux/mm.h?
> > >
> > > I highly recommend against it. The tracepoint code adds a bit of bloat,
> > > and if you inline it, you add that bloat to every use case. Also, it
> >
> > Is it worse than adding function call to my own stub function into
> > inlined function such as get_page(). I implemented it as following.
> >
> > get_page()
> > {
> > atomic_inc()
> > stub_get_page()
> > }
> >
> > stub_get_page() in foo.c
> > {
> > trace_page_ref_get_page()
> > }
>
> Now you just slowed down the fast path. But what you could do is:
>
> get_page()
> {
> atomic_inc();
> if (trace_page_ref_get_page_enabled())
> stub_get_page();
> }
>
> Now that "trace_page_ref_get_page_enabled()" will turn into:
>
> if (static_key_false(&__tracepoint_page_ref_get_page.key)) {
>
> which is a jump label (nop when disabled, a jmp when enabled). That's
> less bloat but doesn't solve the include problem. You still need to add
> the include of that will cause havoc with other tracepoints.
Yes, It also has a include dependency problem so I can't use
trace_page_ref_get_page_enabled() in mm.h. BTW, I tested following
implementation and it works fine.
extern struct tracepoint __tracepoint_page_ref_get_page;
get_page()
{
atomic_inc()
if (static_key_false(&__tracepoint_page_ref_get_page.key))
stub_get_page()
}
This would not slow down fast path although it can't prevent bloat.
I know that it isn't good code practice, but, this page reference
handling functions have complex include dependency so I'm not sure
I can solve it completely. For this special case, can I use
this raw data structure?
Thanks.
next prev parent reply other threads:[~2015-11-24 2:16 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-09 7:23 [PATCH 1/2] mm: introduce page reference manipulation functions Joonsoo Kim
2015-11-09 7:23 ` [PATCH 2/2] mm/page_ref: add tracepoint to track down page reference manipulation Joonsoo Kim
2015-11-10 16:02 ` Michal Nazarewicz
2015-11-18 15:34 ` Vlastimil Babka
2015-11-19 6:50 ` Minchan Kim
2015-11-20 6:33 ` Joonsoo Kim
2015-11-20 16:42 ` Steven Rostedt
2015-11-23 8:28 ` Joonsoo Kim
2015-11-23 14:26 ` Steven Rostedt
2015-11-24 1:45 ` Joonsoo Kim [this message]
2015-12-03 4:16 ` Joonsoo Kim
2015-12-09 20:01 ` Steven Rostedt
2015-12-10 2:50 ` Joonsoo Kim
2015-12-10 3:36 ` Steven Rostedt
2015-12-10 4:07 ` Joonsoo Kim
2015-11-24 1:56 ` Joonsoo Kim
2015-11-09 7:53 ` [PATCH 1/2] mm: introduce page reference manipulation functions Sergey Senozhatsky
2015-11-09 8:00 ` Joonsoo Kim
2015-11-09 11:45 ` Kirill A. Shutemov
2015-11-10 0:28 ` Joonsoo Kim
2015-11-10 15:58 ` Michal Nazarewicz
2016-02-15 3:04 js1304
2016-02-15 3:04 ` [PATCH 2/2] mm/page_ref: add tracepoint to track down page reference manipulation js1304
2016-02-15 5:08 ` Sergey Senozhatsky
2016-02-15 5:28 ` Sergey Senozhatsky
2016-02-15 14:18 ` Joonsoo Kim
2016-02-15 16:07 ` Steven Rostedt
2016-02-16 0:47 ` Joonsoo Kim
2016-02-16 1:16 ` Steven Rostedt
2016-02-18 7:46 ` Joonsoo Kim
2016-02-18 14:20 ` Steven Rostedt
2016-02-18 14:29 ` Steven Rostedt
2016-02-19 0:34 ` Sergey Senozhatsky
2016-02-19 1:39 ` Joonsoo Kim
2016-02-19 1:46 ` Steven Rostedt
2016-02-19 2:15 ` Sergey Senozhatsky
2016-02-19 1:20 ` Joonsoo Kim
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20151124014527.GA32335@js1304-P5Q-DELUXE \
--to=iamjoonsoo.kim@lge.com \
--cc=akpm@linux-foundation.org \
--cc=kirill.shutemov@linux.intel.com \
--cc=linux-api@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@suse.de \
--cc=mina86@mina86.com \
--cc=minchan@kernel.org \
--cc=rostedt@goodmis.org \
--cc=vbabka@suse.cz \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).