linux-kernel - Re: [PATCH v4 03/16] mm: Batch-clear PTE ranges during zap_pte

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Message-ID: <87zfy5zbmu.fsf@nvdebian.thelocal>
Date: Wed, 20 Dec 2023 16:25:07 +1100
From: Alistair Popple <apopple@...dia.com>
To: Ryan Roberts <ryan.roberts@....com>
Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon
 <will@...nel.org>, Ard Biesheuvel <ardb@...nel.org>, Marc Zyngier
 <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, James Morse
 <james.morse@....com>, Suzuki K Poulose <suzuki.poulose@....com>, Zenghui
 Yu <yuzenghui@...wei.com>, Andrey Ryabinin <ryabinin.a.a@...il.com>,
 Alexander Potapenko <glider@...gle.com>, Andrey Konovalov
 <andreyknvl@...il.com>, Dmitry Vyukov <dvyukov@...gle.com>, Vincenzo
 Frascino <vincenzo.frascino@....com>, Andrew Morton
 <akpm@...ux-foundation.org>, Anshuman Khandual
 <anshuman.khandual@....com>, Matthew Wilcox <willy@...radead.org>, Yu Zhao
 <yuzhao@...gle.com>, Mark Rutland <mark.rutland@....com>, David
 Hildenbrand <david@...hat.com>, Kefeng Wang <wangkefeng.wang@...wei.com>,
 John Hubbard <jhubbard@...dia.com>, Zi Yan <ziy@...dia.com>, Barry Song
 <21cnbao@...il.com>, Yang Shi <shy828301@...il.com>,
 linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 03/16] mm: Batch-clear PTE ranges during zap_pte_range()


Ryan Roberts <ryan.roberts@....com> writes:

[...]

> diff --git a/mm/mmu_gather.c b/mm/mmu_gather.c
> index 4f559f4ddd21..39725756e6bf 100644
> --- a/mm/mmu_gather.c
> +++ b/mm/mmu_gather.c
> @@ -47,6 +47,21 @@ static bool tlb_next_batch(struct mmu_gather *tlb)
>  	return true;
>  }
>  
> +unsigned int tlb_reserve_space(struct mmu_gather *tlb, unsigned int nr)
> +{
> +	struct mmu_gather_batch *batch = tlb->active;
> +	unsigned int nr_alloc = batch->max - batch->nr;
> +
> +	while (nr_alloc < nr) {
> +		if (!tlb_next_batch(tlb))
> +			break;
> +		nr_alloc += tlb->active->max;
> +	}
> +
> +	tlb->active = batch;
> +	return nr_alloc;
> +}

Agree this addresses my previous comment nicely, so you can add:

Reviewed-by: Alistair Popple <apopple@...dia.com>

> +
>  #ifdef CONFIG_SMP
>  static void tlb_flush_rmap_batch(struct mmu_gather_batch *batch, struct vm_area_struct *vma)
>  {