linux-kernel - Re: [RFC PATCH 09/16] mm/memory: split non-tlb flushing part from zap_page_range

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Message-ID: <20250306190905.842447-1-sj@kernel.org>
Date: Thu,  6 Mar 2025 11:09:04 -0800
From: SeongJae Park <sj@...nel.org>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: SeongJae Park <sj@...nel.org>,
	"Liam R. Howlett" <howlett@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...hat.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	kernel-team@...a.com,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [RFC PATCH 09/16] mm/memory: split non-tlb flushing part from zap_page_range_single()

On Thu, 6 Mar 2025 10:45:01 -0800 Shakeel Butt <shakeel.butt@...ux.dev> wrote:

> On Wed, Mar 05, 2025 at 10:16:04AM -0800, SeongJae Park wrote:
> > Some of zap_page_range_single() callers such as [process_]madvise() with
> > MADV_DONEED[_LOCKED] cannot batch tlb flushes because
> > zap_page_range_single() does tlb flushing for each invocation.  Split
> > out core part of zap_page_range_single() except mmu_gather object
> > initialization and gathered tlb entries flushing part for such batched
> > tlb flushing usage.
> > 
> > Signed-off-by: SeongJae Park <sj@...nel.org>
> > ---
> >  mm/memory.c | 36 ++++++++++++++++++++++--------------
> >  1 file changed, 22 insertions(+), 14 deletions(-)
> > 
> > diff --git a/mm/memory.c b/mm/memory.c
> > index a838c8c44bfd..aadb2844c701 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -2011,38 +2011,46 @@ void unmap_vmas(struct mmu_gather *tlb, struct ma_state *mas,
> >  	mmu_notifier_invalidate_range_end(&range);
> >  }
> >  
> > -/**
> > - * zap_page_range_single - remove user pages in a given range
> > - * @vma: vm_area_struct holding the applicable pages
> > - * @address: starting address of pages to zap
> > - * @size: number of bytes to zap
> > - * @details: details of shared cache invalidation
> > - *
> > - * The range must fit into one VMA.
> > - */
> > -void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
> > +static void unmap_vma_single(struct mmu_gather *tlb,
> > +		struct vm_area_struct *vma, unsigned long address,
> >  		unsigned long size, struct zap_details *details)
> >  {
> 
> Please add kerneldoc for this function and explicitly specify that tlb
> can not be NULL. Maybe do that in the patch where you make it
> non-static.

Thank you for this nice suggestion, I will do so in the next version.


Thanks,
SJ