From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750978AbdALQro (ORCPT ); Thu, 12 Jan 2017 11:47:44 -0500 Received: from mga09.intel.com ([134.134.136.24]:35667 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750733AbdALQrn (ORCPT ); Thu, 12 Jan 2017 11:47:43 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.33,219,1477983600"; d="asc'?scan'208";a="1082239820" Date: Thu, 12 Jan 2017 08:47:18 -0800 From: Tim Chen To: Andi Kleen Cc: Andrew Morton , "Huang, Ying" , dave.hansen@intel.com, aaron.lu@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hugh Dickins , Shaohua Li , Minchan Kim , Rik van Riel , Andrea Arcangeli , "Kirill A . Shutemov" , Vladimir Davydov , Johannes Weiner , Michal Hocko , Hillf Danton , Christian Borntraeger , Jonathan Corbet Subject: Re: [PATCH v5 3/9] mm/swap: Split swap cache into 64MB trunks Message-ID: <20170112164717.GA26499@linux.intel.com> Reply-To: tim.c.chen@linux.intel.com References: <735bab895e64c930581ffb0a05b661e01da82bc5.1484082593.git.tim.c.chen@linux.intel.com> <20170111150940.25d951a121a62e1b7eff6f8d@linux-foundation.org> <20170111231937.GH8388@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="Q68bSM7Ycu6FN28Q" Content-Disposition: inline In-Reply-To: <20170111231937.GH8388@tassilo.jf.intel.com> User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --Q68bSM7Ycu6FN28Q Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Jan 11, 2017 at 03:19:37PM -0800, Andi Kleen wrote: > > Switching from a single radix-tree to an array of radix-trees to reduce > > contention seems a bit hacky. That we can do this and have everything > > continue to work tells me that we're simply using an inappropriate data > > structure to hold this info. >=20 > What would you use instead? I agree that this approach is a bit hacky. However, it is pretty effective and simple. If later on we come up with a better solution to scale modfication of the radix tree, we can collapse the radix trees. I think developing a scalable radix tree with write modifications will take quite a while and is a non-trivial effort. With almost memory speed SSDs coming on the market soon, I think having a workable solution now and optimizing it for long term is reasonabale. Tim --Q68bSM7Ycu6FN28Q Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIcBAEBAgAGBQJYd7MVAAoJEKJntYqi1rhJ37gP+gMpkfG7NapantPNemSYIdLh b/h5HDj83mCZ5kZjygBKkYtSn+IbBbMWdMmtKRZlDBcKfrx+AS50Rbdw8MoJqGsv i0p1NwNv9gdhETq3NdT3EVJA3Ot2oj8wDPf4hRvJNPuoz+2OeLZfN5rsJ7GHlFMz 0POIJZVE3Qxw95A4y4IHaf2il4kc/ATDBUA03eSCL/fw/EOPB9vgY19sdxOcVvGP wpn0B3u/FS3OzFZ6G/nLKyof0dAYgHQ9wC6j1Nv4+mEZmlHBCa2gjYgMakSjKuXN T+BV5fLOef7eDdQnUeKuvknxkTrSfoFo/004cgM3FHabN3O8GmZmUVqt1bdh0e1g 45hgOEZsJNdPXvA7Ap9JyIso9zGnPhvgJKdnBS6bHVLR2LCR8BiIlswxx783elM/ +lvB0Ije8zj4vOF5mfQXk/7Mi8UAAgrk9nEdDRDlPkgNfGursTF88dfhJpcsNngV eMCfYJwPoCNLLEeTCnsR9U3s9Gws9JN1JpoH3A9hXUdNpJLK3WRqkJnSOk1D0tfK jKosZiQC8y+aQ4iuzguLqmmjzereMLfBi5BXxpiek87r7bwKL5e/+dv/wGlaHeEu pv1Tv5Q1+E+dbJ2z4ipNCxpxXitAFJr8ul4aFcUVrhoGoe2g84D2ykzB786+emS7 gPm4I7//CrNh8TXGqwfV =FkNN -----END PGP SIGNATURE----- --Q68bSM7Ycu6FN28Q--