From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [103.22.144.67]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 192011A03F8 for ; Thu, 29 Oct 2015 14:00:33 +1100 (AEDT) Date: Thu, 29 Oct 2015 14:00:29 +1100 From: Paul Mackerras To: "Aneesh Kumar K.V" Cc: benh@kernel.crashing.org, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org Subject: Re: [RFC PATCH 0/7] Remove 4k subpage tracking with hash 64K config Message-ID: <20151029030029.GA31681@fergus.ozlabs.ibm.com> References: <1445371953-9627-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1445371953-9627-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, Oct 21, 2015 at 01:42:26AM +0530, Aneesh Kumar K.V wrote: > Hi, > > This patch series is on top of the series posted at > > https://lists.ozlabs.org/pipermail/linuxppc-dev/2015-October/135299.html > "[PATCH V4 00/31] powerpc/mm: Update page table format for book3s 64". In this > series we remove 4k subpage tracking with 64K config. Instead we do a hash > table lookup to get the slot information of 4k hash ptes. This also allow us > to remove real_pte_t. Side effect of the change is that a specific 4k slot > lookup can result in multiple H_READ hcalls. But that should only impact > when we are using 4K subpages which should be rare. > > NOTE: I only tested this on systemsim. Wanted to get this out to get early > feedback. I tried this on a quad G5 and it seems to work just fine. On a kernel compile test there was very little difference in speed - I measured about 0.4% slowdown but that may not be statistically significant. This was with 64k pages configured and THP enabled. Paul.