linux-kernel - Re: [RFC PATCH 2/7] mm/vmalloc: Track which page-table levels were modified

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Message-ID: <20200508212321.GR8135@suse.de>
Date:   Fri, 8 May 2020 23:23:21 +0200
From:   Joerg Roedel <jroedel@...e.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Joerg Roedel <joro@...tes.org>, x86@...nel.org, hpa@...or.com,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>, rjw@...ysocki.net,
        Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...nel.org>, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [RFC PATCH 2/7] mm/vmalloc: Track which page-table levels were
 modified

On Fri, May 08, 2020 at 09:10:48PM +0200, Peter Zijlstra wrote:
> On Fri, May 08, 2020 at 04:40:38PM +0200, Joerg Roedel wrote:
> > +	if (mask & ARCH_PAGE_TABLE_SYNC_MASK)
> > +		arch_sync_kernel_mappings(start, end);
> 
> So you're relying on the compiler DCE'ing the call in the 'normal' case.
> 
> Works I suppose, but I went over the patches twice to look for a default
> implementation of it before I figured that out ...

Yes, works on all architectures I compile-tested this on, with gcc-9.3.
I should probably add a comment about that.


	Joerg