From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Micay Subject: Re: [PATCH v3] mm: add mremap flag for preserving the old mapping Date: Thu, 02 Oct 2014 17:09:39 -0400 Message-ID: <542DBF13.6000305@gmail.com> References: <1412052900-1722-1-git-send-email-danielmicay@gmail.com> <542A79AF.8060602@gmail.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="PRlCVIkmvMIs5cCoIexuIIqIjW92QRa2D" Return-path: In-Reply-To: Sender: owner-linux-mm@kvack.org To: Andy Lutomirski Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Andrew Morton , Jason Evans , Linux API List-Id: linux-api@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --PRlCVIkmvMIs5cCoIexuIIqIjW92QRa2D Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 30/09/14 01:49 PM, Andy Lutomirski wrote: >=20 > I think it might pay to add an explicit vm_op to authorize > duplication, especially for non-cow mappings. IOW this kind of > extension seems quite magical for anything that doesn't have the > normal COW semantics, including for plain old read-only mappings. Adding a vm_ops table to MAP_PRIVATE|MAP_ANONYMOUS mappings has a significant performance impact. I haven't yet narrowed it down, but there's at least one code path a check of `!vma->vm_ops` for the fast path. One is for transparent huge page faults, so the performance impact makes sense. I'll use a simpler implementation for now since the requirements are very narrow / simple. --PRlCVIkmvMIs5cCoIexuIIqIjW92QRa2D Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBAgAGBQJULb8WAAoJEPnnEuWa9fIqSNAP/A7LCl/XGzXIE2tl5P6OOodp oTI8okG15yxG4jXYOH7dT5//3qdvkeU5mU86/IOde+qmts2i5W+wNnM1rYHyOZka hil/u1vF3flo+SiI47r9alh2JOyS7Yl51VFNQZ2ExIX9eUdAAahhdASCAQDia/D8 bITv3Z5XSGPRCxglo6vUYjRgv1l9Hrx+riwcwe9ceyNFx6Q7dD9/FzDs0nAu4Oy7 45caIcaVlBUpKiyhjwWFYF3wFO1J3LTC6zJyaA1TkbCTC5mbokGMDO6ghvGrzLE7 /jZIxJdsoNp3ifjgXlRg+9nO3UAP3LwsueHJlWuC2Xn5iNq9XNWyvxSvtWND/30d TMwLS4ox1UFfd3TQhla100j2h0kAJECL+l2Rm61uNWlwN3+SdnzhLNHN9nKC2gAA uuhFaM+jNWwSjN3d8NMM2L01eZZi1Fy18jcb/iGEDAZ3O83rYBIGy2WZJTJVQOnc xjxyQl7NuBLugIUAkSC5OqJGEQ84ur56wX1HmlRbV7sdd8bbpNuXQS3qZuoY+p8H fQSCW3w4hJ8mQBS4l5MZ/Oc44XuNNdQbEzL60Af0uxQbC46C83tJyqOUHKLysKnH 7lnEsm7tIXtisw5mg9blovJUSOZ5ZL5MshD0kdSLjkPUhjXm5bBJFsC3b2MsmI/A MUa1auMJAdsi3LBa3uw6 =mK1z -----END PGP SIGNATURE----- --PRlCVIkmvMIs5cCoIexuIIqIjW92QRa2D-- -- 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