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Date:      Thu, 16 Feb 2006 20:30:39 -0500
From:      Kris Kennaway <kris@obsecurity.org>
To:        Mike Jakubik <mikej@rogers.com>
Cc:        Giorgos Keramidas <keramida@ceid.upatras.gr>, Dmitry Pryanishnikov <dmitry@atlantis.dp.ua>, freebsd-current@freebsd.org, David Xu <davidxu@freebsd.org>, Brian Candler <B.Candler@pobox.com>
Subject:   Re: Virtual memory consumption (both user and kernel) in modern	CURRENT
Message-ID:  <20060217013039.GA31540@xor.obsecurity.org>
In-Reply-To: <43F525A6.3080701@rogers.com>
References:  <20060215024339.N22450@atlantis.atlantis.dp.ua> <43F29BF5.4060300@freebsd.org> <20060216123548.GA35910@uk.tiscali.com> <20060216135138.GA16669@flame.pc> <43F525A6.3080701@rogers.com>

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On Thu, Feb 16, 2006 at 08:23:50PM -0500, Mike Jakubik wrote:
> Giorgos Keramidas wrote:
> >On 2006-02-16 12:35, Brian Candler <B.Candler@pobox.com> wrote:
> > =20
> >>On Wed, Feb 15, 2006 at 11:11:49AM +0800, David Xu wrote:
> >>   =20
> >>>>1) Is it normal that virtual memory size for almost every non-kernel
> >>>>process
> >>>>  is close to 50Mb now:
> >>>>
> >>>>   ftp://external.atlantis.dp.ua/FreeBSD/CURRENT/top.txt
> >>>>
> >>>>  Is it miscalculation or real growth of virtual address space?
> >>>>       =20
> >>>I believe this is the new malloc code in libc, I am seeing this on my
> >>>Athlon64 machine, now it likes swap memory, in the old days, it seldom
> >>>touched it.
> >>>     =20
> >>IIRR, the new malloc grabs 32MB immediately. However, I'd hope that=20
> >>doesn't
> >>mean that 32MB of pages are actually touched, and then get swapped out =
to
> >>disk. If it does, I'm staying on FreeBSD 6.0 :-)
> >>   =20
> >
> >I don't think so.
> >
> >At least, not unless you are using the debugging features of malloc(),
> >which can result in all pages getting touched (i.e. if the "J" option is
> >enabled, to set all newly-allocated bytes to 0xa5, which is very helpful
> >when trying to catch accesses to uninitialized pointers).
> >
> >It's all a matter of what you are prepared to trade-off and why, I guess=
 :)
> > =20
>=20
> And what am i trading off here? I have "/etc/malloc.conf@ -> ajz" and my=
=20
> memory usage has gone up the roof. My system used to be swap free, and=20
> now its swapping over 40 MB. Can someone explain to me why this new=20
> malloc is better? I don't see any speed improvements.

It's a couple of orders of magnitude faster for threaded binaries.
See earlier posts by the author for extensive discussion.

Kris

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