linux-kernel - Re: [PATCH 13/12] ksm: fix munlock during exit

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Message-ID: <4A96DFFF.1040501@redhat.com>
Date:	Thu, 27 Aug 2009 22:35:27 +0300
From:	Izik Eidus <ieidus@...hat.com>
To:	Hugh Dickins <hugh.dickins@...cali.co.uk>
CC:	Andrea Arcangeli <aarcange@...hat.com>,
	Rik van Riel <riel@...hat.com>,
	Chris Wright <chrisw@...hat.com>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Justin M. Forbes" <jmforbes@...uxtx.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 13/12] ksm: fix munlock during exit_mmap deadlock

Hugh Dickins wrote:
>
> It may be that MADV_UNMERGEABLE isn't really needed (I think I even
> admitted once that probably nobody would use it other than we testing
> it).  Yet I hesitate to rip it out: somehow it still seems right to
> have it in there.  Why did you have unregistering in the /dev/ksm KSM?
>   

It was more to give possiblaty to applications save cpu cycles of ksmd 
so it wont continue to scan memory regions that don`t need ksm anymore,
As you said if someone will ever use it?, have no idea...

>   
> I didn't seem idiotic to me, but I hadn't realized the ksmd timelapse
> uncertainty Andrea points out.  Well, I'm not keen to change the way
> it's working at present, but I do think you're right to question all
> these aspects of unmerging.
>   

Yes lets keep it like that, UNMERGEABLE sound anyway like something that 
going to break the pages..., we can always add later STOPMERGE as a call 
that tell ksm to stop merge the pages but not break the shared pages...

> Hugh
>   

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