linux-kernel - Re: [RFC 00/20] TLB batching consolidation and enhancements

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Message-ID: <34961389-0BFD-4F30-84AF-FB2FE5B07949@vmware.com>
Date:   Sun, 31 Jan 2021 01:08:08 +0000
From:   Nadav Amit <namit@...are.com>
To:     Andy Lutomirski <luto@...nel.org>
CC:     Linux-MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "linux-csky@...r.kernel.org" <linux-csky@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Nick Piggin <npiggin@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>, X86 ML <x86@...nel.org>,
        Yu Zhao <yuzhao@...gle.com>
Subject: Re: [RFC 00/20] TLB batching consolidation and enhancements

> On Jan 30, 2021, at 4:39 PM, Andy Lutomirski <luto@...nel.org> wrote:
> 
> On Sat, Jan 30, 2021 at 4:16 PM Nadav Amit <nadav.amit@...il.com> wrote:
>> From: Nadav Amit <namit@...are.com>
>> 
>> There are currently (at least?) 5 different TLB batching schemes in the
>> kernel:
>> 
>> 1. Using mmu_gather (e.g., zap_page_range()).
>> 
>> 2. Using {inc|dec}_tlb_flush_pending() to inform other threads on the
>>   ongoing deferred TLB flush and flushing the entire range eventually
>>   (e.g., change_protection_range()).
>> 
>> 3. arch_{enter|leave}_lazy_mmu_mode() for sparc and powerpc (and Xen?).
>> 
>> 4. Batching per-table flushes (move_ptes()).
>> 
>> 5. By setting a flag on that a deferred TLB flush operation takes place,
>>   flushing when (try_to_unmap_one() on x86).
> 
> Are you referring to the arch_tlbbatch_add_mm/flush mechanism?

Yes.