linux-kernel - Re: [RFC PATCH 0/7] mm: Get rid of vmalloc_sync

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Message-ID: <20200511073134.GD2957@hirez.programming.kicks-ass.net>
Date:   Mon, 11 May 2020 09:31:34 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Joerg Roedel <jroedel@...e.de>, 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 0/7] mm: Get rid of vmalloc_sync_(un)mappings()

On Sat, May 09, 2020 at 06:11:57PM -0700, Matthew Wilcox wrote:
> Iterating an XArray (whether the entire thing
> or with marks) is RCU-safe and faster than iterating a linked list,
> so this should solve the problem?

It can hardly be faster if you want all elements -- which is I think the
case here. We only call into this if we change an entry, and then we
need to propagate that change to all.