From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4615B5D9.7060703@redhat.com> Date: Thu, 05 Apr 2007 19:52:09 -0700 From: Ulrich Drepper MIME-Version: 1.0 Subject: Re: missing madvise functionality References: <46128051.9000609@redhat.com> <46128CC2.9090809@redhat.com> <20070403172841.GB23689@one.firstfloor.org> <20070403125903.3e8577f4.akpm@linux-foundation.org> <4612B645.7030902@redhat.com> <20070403202937.GE355@devserv.devel.redhat.com> <4614A5CC.5080508@redhat.com> <46151F73.50602@redhat.com> <4615B043.8060001@yahoo.com.au> In-Reply-To: <4615B043.8060001@yahoo.com.au> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig142F53141530ABD4FA3327D3" Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Rik van Riel , Jakub Jelinek , Andrew Morton , Andi Kleen , Linux Kernel , linux-mm@kvack.org, Hugh Dickins List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig142F53141530ABD4FA3327D3 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Nick Piggin wrote: > Cool. According to my thinking, madvise(MADV_DONTNEED) even in today's > kernels using down_write(mmap_sem) for MADV_DONTNEED is better than > mmap/mprotect, which have more fundamental locking requirements, more > overhead and no benefits (except debugging, I suppose). It's a tiny bit faster, see http://people.redhat.com/drepper/dontneed.png I just ran it once so the graph is not smooth. This is on a UP dual core machine. Maybe tomorrow I'll turn on the big 4p machine. I would have to see dramatically different results on the big machine to make me change the libc code. The reason is that there is a big drawback= =2E So far, when we allocate a new arena, we allocate address space with PROT_NONE and only when we need memory the protection is changed to PROT_READ|PROT_WRITE. This is the advantage of catching wild pointer accesses. --=20 =E2=9E=A7 Ulrich Drepper =E2=9E=A7 Red Hat, Inc. =E2=9E=A7 444 Castro St = =E2=9E=A7 Mountain View, CA =E2=9D=96 --------------enig142F53141530ABD4FA3327D3 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org iD8DBQFGFbXZ2ijCOnn/RHQRAt06AKCJzuZsl2Ba8VCRWWUc2+BbSQ+16ACgnIGM 6NuLcq3+/gFllhoYBNJ0AtU= =63qB -----END PGP SIGNATURE----- --------------enig142F53141530ABD4FA3327D3-- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org