From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qg0-f45.google.com (mail-qg0-f45.google.com [209.85.192.45]) by kanga.kvack.org (Postfix) with ESMTP id 73E8F6B0005 for ; Wed, 6 Apr 2016 16:33:53 -0400 (EDT) Received: by mail-qg0-f45.google.com with SMTP id f105so22585300qge.2 for ; Wed, 06 Apr 2016 13:33:53 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id q196si3422568qha.43.2016.04.06.13.33.52 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 06 Apr 2016 13:33:52 -0700 (PDT) Message-ID: <1459974829.28435.6.camel@redhat.com> Subject: Re: [PATCH 1/1] ksm: introduce ksm_max_page_sharing per page deduplication limit From: Rik van Riel Date: Wed, 06 Apr 2016 16:33:49 -0400 In-Reply-To: <1447181081-30056-2-git-send-email-aarcange@redhat.com> References: <1447181081-30056-1-git-send-email-aarcange@redhat.com> <1447181081-30056-2-git-send-email-aarcange@redhat.com> Content-Type: multipart/signed; micalg="pgp-sha1"; protocol="application/pgp-signature"; boundary="=-Z5cNlTHiW6Jw5GTxWqiV" Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli , Hugh Dickins , Davidlohr Bueso Cc: linux-mm@kvack.org, Petr Holasek , Andrew Morton , Arjan van de Ven --=-Z5cNlTHiW6Jw5GTxWqiV Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, 2015-11-10 at 19:44 +0100, Andrea Arcangeli wrote: > Without a max deduplication limit for each KSM page, the list of the > rmap_items associated to each stable_node can grow infinitely > large. >=20 > During the rmap walk each entry can take up to ~10usec to process > because of IPIs for the TLB flushing (both for the primary MMU and > the > secondary MMUs with the MMU notifier). With only 16GB of address > space > shared in the same KSM page, that would amount to dozens of seconds > of > kernel runtime. Silly question, but could we fix this problem by building up a bitmask of all CPUs that have a page-with-high-mapcount mapped, and simply send out a global TLB flush to those CPUs once we have changed the page tables, instead of sending out IPIs at every page table change? --=20 All rights reversed --=-Z5cNlTHiW6Jw5GTxWqiV Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAABAgAGBQJXBXKtAAoJEM553pKExN6DXasIAJ7STrI+JVrogVriiXP7sNB+ H/odmLSyLCPQkAg/a+9GpyoqrJ+ouk4rRT+HiP3DtrJ7+0od4BC+iHMuTDo+Hw6x vMefL4k0NhKgiHPqsEXvmitNxZEz4bhJpkVXvEr+KBuZm39iTSvmHZNjWqA30UO7 FdWwNNGt5N310/hSPc26G4U1Qa3TyuUJHleThNQEdTTzX8YTjqR8wciLbKaSTIB1 Rt+eNwziiR9Im4ZXsHpFLaD3MWAkqSmJuRBQgUpHjQr5zWMz3aOJvUgjKkW5LDBe UeV54ZS5QoSL3tVLaqpGxIXjykPm3pJ+LWNjLJHaUiSI0brt6CXkKft67uPvVNE= =CdDD -----END PGP SIGNATURE----- --=-Z5cNlTHiW6Jw5GTxWqiV-- -- 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