From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (bilbo.ozlabs.org [103.22.144.67]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3z2yWF5hrRzF07W for ; Fri, 22 Dec 2017 16:59:05 +1100 (AEDT) Received: from ozlabs.org (bilbo.ozlabs.org [103.22.144.67]) by bilbo.ozlabs.org (Postfix) with ESMTP id 3z2yWF4gmRz8t8G for ; Fri, 22 Dec 2017 16:59:05 +1100 (AEDT) Received: from mail-ua0-x22a.google.com (mail-ua0-x22a.google.com [IPv6:2607:f8b0:400c:c08::22a]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3z2yWF13dgz9sBZ for ; Fri, 22 Dec 2017 16:59:04 +1100 (AEDT) Received: by mail-ua0-x22a.google.com with SMTP id v22so1229848uaj.1 for ; Thu, 21 Dec 2017 21:59:04 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <87608zpd10.fsf@concordia.ellerman.id.au> References: <20171220042520.7946-1-mpe@ellerman.id.au> <87608zpd10.fsf@concordia.ellerman.id.au> From: Balbir Singh Date: Fri, 22 Dec 2017 16:59:02 +1100 Message-ID: Subject: Re: [PATCH] powerpc/pseries: Increase memory block size to 1GB on radix To: Michael Ellerman Cc: linuxppc-dev , Aneesh Kumar KV , Anton Blanchard , David Gibson Content-Type: text/plain; charset="UTF-8" List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, Dec 22, 2017 at 4:06 PM, Michael Ellerman wrote: > Michael Ellerman writes: > >> When we're using the Radix MMU we map the kernel linear mapping with >> 1G pages. That means we must do memory hot remove in blocks of at >> least that size. Otherwise the linear mapping can end up not mapping >> all of memory because we've removed part of a 1G region but unmapped >> the entire 1G region from the linear mapping. >> >> Currently on pseries we consult the device tree to find out the the >> "LMB" (Logical Memory Block) size. This is the unit of memory hotplug >> communicated to us by the hypervisor, but it does not take into >> account anything the kernel has done itself, such as use 1G pages for >> the linear mapping. > > This patch failed to survive contact with reality. ie. it doesn't work. > > NAK. I have patches to split the size of a region, I guess the right thing to do is to split the size of mapping during hotplug. I can look at doing that once I am back. What broke for you during testing? Balbir Singh.