LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Sergei Rogachev <rogachevsergei@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: iamjoonsoo.kim@lge.com, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/1] mm/page_ext: remove unnecessary stack_trace field
Date: Wed, 28 Jan 2015 23:08:47 +0400	[thread overview]
Message-ID: <20150128230847.16cc8e4fbb5f601dc667d94d@gmail.com> (raw)
In-Reply-To: <20150127144319.f3a161e5f5d562a0a605371e@linux-foundation.org>

On Tue, 27 Jan 2015 14:43:19 -0800
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Tue, 27 Jan 2015 00:52:12 +0300 Sergei Rogachev <rogachevsergei@gmail.com> wrote:
> 
> > Page owner uses the page_ext structure to keep meta-information
> > for every page in the system. The structure also contains a field
> > of type 'struct stack_trace', page owner uses this field during
> > invocation of the function save_stack_trace. It is easy to notice
> > that keeping a copy of this structure for every page in the system
> > is very inefficiently in terms of memory.
> > 
> > The patch removes this unnecessary field of page_ext and forces
> > page owner to use a stack_trace structure allocated on the stack.
> > 
> 
> Fair enough.
> 
> What do you think of the below tweaks?  Seems a bit neater, and it will
> cause all unmentioned fields to be zeroed out.  It's not a bug to leave
> .max_entries uninitialised in print_page_owner(), but it's nice not to
> leave loose ends.

Yes, with your fix the code looks much better!

> 
> --- a/mm/page_owner.c~mm-page_ext-remove-unnecessary-stack_trace-field-fix
> +++ a/mm/page_owner.c
> @@ -59,15 +59,14 @@ void __reset_page_owner(struct page *pag
>  
>  void __set_page_owner(struct page *page, unsigned int order, gfp_t gfp_mask)
>  {
> -	struct page_ext *page_ext;
> -	struct stack_trace trace;
> +	struct page_ext *page_ext = lookup_page_ext(page);
> +	struct stack_trace trace = {
> +		.nr_entries = 0,
> +		.max_entries = ARRAY_SIZE(page_ext->trace_entries),
> +		.entries = &page_ext->trace_entries[0],
> +		.skip = 3,
> +	};
>  
> -	page_ext = lookup_page_ext(page);
> -
> -	trace.nr_entries = 0;
> -	trace.max_entries = ARRAY_SIZE(page_ext->trace_entries);
> -	trace.entries = &page_ext->trace_entries[0];
> -	trace.skip = 3;
>  	save_stack_trace(&trace);
>  
>  	page_ext->order = order;
> @@ -83,8 +82,11 @@ print_page_owner(char __user *buf, size_
>  {
>  	int ret;
>  	int pageblock_mt, page_mt;
> -	struct stack_trace trace;
>  	char *kbuf;
> +	struct stack_trace trace = {
> +		.nr_entries = page_ext->nr_entries,
> +		.entries = &page_ext->trace_entries[0],
> +	};
>  
>  	kbuf = kmalloc(count, GFP_KERNEL);
>  	if (!kbuf)
> @@ -122,9 +124,6 @@ print_page_owner(char __user *buf, size_
>  	if (ret >= count)
>  		goto err;
>  
> -	trace.nr_entries = page_ext->nr_entries;
> -	trace.entries = &page_ext->trace_entries[0];
> -
>  	ret += snprint_stack_trace(kbuf + ret, count - ret, &trace, 0);
>  	if (ret >= count)
>  		goto err;
> _
> 

      reply	other threads:[~2015-01-28 20:58 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-26 21:52 [PATCH 0/1] " Sergei Rogachev
2015-01-26 21:52 ` [PATCH 1/1] " Sergei Rogachev
2015-01-27  8:36   ` Joonsoo Kim
2015-01-27 22:43   ` Andrew Morton
2015-01-28 19:08     ` Sergei Rogachev [this message]

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=20150128230847.16cc8e4fbb5f601dc667d94d@gmail.com \
    --to=rogachevsergei@gmail.com \
    --cc=akpm@linux-foundation.org \
    --cc=iamjoonsoo.kim@lge.com \
    --cc=linux-kernel@vger.kernel.org \
    --subject='Re: [PATCH 1/1] mm/page_ext: remove unnecessary stack_trace field' \
    /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

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).