linux-kernel - Re: [PATCH 01/13] mm: Update ptep_get

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Message-Id: <1701B847-EE00-474A-ACF2-C4051884F8F1@gmail.com>
Date:   Thu, 27 Oct 2022 10:30:11 -0700
From:   Nadav Amit <nadav.amit@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Jann Horn <jannh@...gle.com>, John Hubbard <jhubbard@...dia.com>,
        X86 ML <x86@...nel.org>, Matthew Wilcox <willy@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        jroedel@...e.de, ubizjak@...il.com
Subject: Re: [PATCH 01/13] mm: Update ptep_get_lockless()s comment

On Oct 27, 2022, at 12:27 AM, Peter Zijlstra <peterz@...radead.org> wrote:

>> One alternative may be using mm_tlb_flush_pending() when setting a new PTE
>> to check for pending flushes and flushing the TLB if that is the case. This
>> is somewhat similar to what ptep_clear_flush() does. Anyhow, I guess this
>> might induce some overheads. As noted before, it is possible to track
>> pending TLB flushes in VMA/page-table granularity, with different tradeoffs
>> of overheads.
> 
> Right; I just don't believe in VMAs for this, they're *waaay* to big.

Well, I did it for VMA in an RFC only because I was pushed. I thought and do
think that page-table granularity is the right one.