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From: "Stephen C. Tweedie" <sct@redhat.com>
To: Shuvabrata Ganguly <sganguly@cse.iitkgp.ernet.in>
Cc: "Stephen C. Tweedie" <sct@redhat.com>, linux MM <linux-mm@kvack.org>
Subject: Re: Question about swap_in() in 2.2.16 ....
Date: Fri, 10 Nov 2000 09:56:43 +0000	[thread overview]
Message-ID: <20001110095643.A15453@redhat.com> (raw)
In-Reply-To: <3A0B7829.B9F33ACA@cse.iitkgp.ernet.in>; from sganguly@cse.iitkgp.ernet.in on Thu, Nov 09, 2000 at 11:23:05PM -0500

Hi,

On Thu, Nov 09, 2000 at 11:23:05PM -0500, Shuvabrata Ganguly wrote:
> "Stephen C. Tweedie" wrote:
> > > Now this creates a read-only mapping  even if the access was a "write
> > > acess"  ( if the page is shared ). Doesnt this mean that an additional
> > > "write-protect" fault will be taken immediately when the process tries
> > > to write again ?
> >
> > Yes.
> 
> Then why dont we give it a private page in the first place ?

Normal copy-on-write is an extremely performance-critical code path.
It's really not worth the trouble of adding extra code to it to make
the swapin page fault do the same copy-on-write immediately, because
swapin simply is not that important for performance.

--Stephen
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      reply	other threads:[~2000-11-10  9:56 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2000-11-08  6:32 Shuvabrata Ganguly
2000-11-08 10:05 ` Stephen C. Tweedie
2000-11-10  4:23   ` Shuvabrata Ganguly
2000-11-10  9:56     ` Stephen C. Tweedie [this message]

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