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

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Message-ID: <20200511074243.GE2957@hirez.programming.kicks-ass.net>
Date:   Mon, 11 May 2020 09:42:43 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Joerg Roedel <jroedel@...e.de>, Joerg Roedel <joro@...tes.org>,
        X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Rafael J. Wysocki" <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>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>
Subject: Re: [RFC PATCH 0/7] mm: Get rid of vmalloc_sync_(un)mappings()

On Sat, May 09, 2020 at 12:05:29PM -0700, Andy Lutomirski wrote:

> On x86_64, the only real advantage is that the handful of corner cases
> that make vmalloc faults unpleasant (mostly relating to vmap stacks)
> go away.  On x86_32, a bunch of mind-bending stuff (everything your
> series deletes but also almost everything your series *adds*) goes
> away.  There may be a genuine tiny performance hit on 2-level systems
> due to the loss of huge pages in vmalloc space, but I'm not sure I
> care or that we use them anyway on these systems.  And PeterZ can stop
> even thinking about RCU.
> 
> Am I making sense?

I think it'll work for x86_64 and that is really all I care about :-)