linux-kernel - Re: [PATCH v2 11/11] hugetlb: batch TLB flushes when restoring vmemmap

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Message-ID: <20230907185844.GF3640@monkey>
Date:   Thu, 7 Sep 2023 11:58:44 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Muchun Song <muchun.song@...ux.dev>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Joao Martins <joao.m.martins@...cle.com>,
        Muchun Song <songmuchun@...edance.com>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        David Rientjes <rientjes@...gle.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Naoya Horiguchi <naoya.horiguchi@...ux.dev>,
        Michal Hocko <mhocko@...e.com>,
        Matthew Wilcox <willy@...radead.org>,
        Xiongchun Duan <duanxiongchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 11/11] hugetlb: batch TLB flushes when restoring
 vmemmap

On 09/07/23 14:58, Muchun Song wrote:
> 
> 
> On 2023/9/6 05:44, Mike Kravetz wrote:
> > Update the hugetlb_vmemmap_restore path to take a 'batch' parameter that
> 
> s/batch/flags/g
> 
> And it should be reworked since the parameter has been changed.

Yes.

> 
> > indicates restoration is happening on a batch of pages.  When set, use
> > the existing mechanism (VMEMMAP_NO_TLB_FLUSH) to delay TLB flushing.
> > The routine hugetlb_vmemmap_restore_folios is the only user of this new
> > batch parameter and it will perform a global flush after all vmemmap is
> > restored.
> > 
> > Signed-off-by: Joao Martins <joao.m.martins@...cle.com>
> > Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
> > ---
> >   mm/hugetlb_vmemmap.c | 37 +++++++++++++++++++++++--------------
> >   1 file changed, 23 insertions(+), 14 deletions(-)
> > 
> > diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> > index 8c85e2c38538..11fda9d061eb 100644
> > --- a/mm/hugetlb_vmemmap.c
> > +++ b/mm/hugetlb_vmemmap.c
> > @@ -458,17 +458,19 @@ static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
> >    * @end:	end address of the vmemmap virtual address range that we want to
> >    *		remap.
> >    * @reuse:	reuse address.
> > + * @flags:	modify behavior for bulk operations
> >    *
> >    * Return: %0 on success, negative error code otherwise.
> >    */
> >   static int vmemmap_remap_alloc(unsigned long start, unsigned long end,
> > -			       unsigned long reuse)
> > +			       unsigned long reuse, unsigned long flags)
> >   {
> >   	LIST_HEAD(vmemmap_pages);
> >   	struct vmemmap_remap_walk walk = {
> >   		.remap_pte	= vmemmap_restore_pte,
> >   		.reuse_addr	= reuse,
> >   		.vmemmap_pages	= &vmemmap_pages,
> > +		.flags		= flags,
> >   	};
> >   	/* See the comment in the vmemmap_remap_free(). */
> > @@ -490,17 +492,7 @@ EXPORT_SYMBOL(hugetlb_optimize_vmemmap_key);
> >   static bool vmemmap_optimize_enabled = IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON);
> >   core_param(hugetlb_free_vmemmap, vmemmap_optimize_enabled, bool, 0);
> > -/**
> > - * hugetlb_vmemmap_restore - restore previously optimized (by
> > - *			     hugetlb_vmemmap_optimize()) vmemmap pages which
> > - *			     will be reallocated and remapped.
> > - * @h:		struct hstate.
> > - * @head:	the head page whose vmemmap pages will be restored.
> > - *
> > - * Return: %0 if @head's vmemmap pages have been reallocated and remapped,
> > - * negative error code otherwise.
> > - */
> > -int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
> > +static int __hugetlb_vmemmap_restore(const struct hstate *h, struct page *head, unsigned long flags)
> >   {
> >   	int ret;
> >   	unsigned long vmemmap_start = (unsigned long)head, vmemmap_end;
> > @@ -521,7 +513,7 @@ int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
> >   	 * When a HugeTLB page is freed to the buddy allocator, previously
> >   	 * discarded vmemmap pages must be allocated and remapping.
> >   	 */
> > -	ret = vmemmap_remap_alloc(vmemmap_start, vmemmap_end, vmemmap_reuse);
> > +	ret = vmemmap_remap_alloc(vmemmap_start, vmemmap_end, vmemmap_reuse, flags);
> >   	if (!ret) {
> >   		ClearHPageVmemmapOptimized(head);
> >   		static_branch_dec(&hugetlb_optimize_vmemmap_key);
> > @@ -530,6 +522,21 @@ int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
> >   	return ret;
> >   }
> > +/**
> > + * hugetlb_vmemmap_restore - restore previously optimized (by
> > + *			     hugetlb_vmemmap_optimize()) vmemmap pages which
> > + *			     will be reallocated and remapped.
> > + * @h:		struct hstate.
> > + * @head:	the head page whose vmemmap pages will be restored.
> > + *
> > + * Return: %0 if @head's vmemmap pages have been reallocated and remapped,
> > + * negative error code otherwise.
> > + */
> > +int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
> > +{
> > +	return __hugetlb_vmemmap_restore(h, head, 0UL);
> 
> UL suffix could be drooped.

Thanks, will fix both in next version.
-- 
Mike Kravetz