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From: Jason Gunthorpe <jgg@nvidia.com>
To: Baolu Lu <baolu.lu@linux.intel.com>
Cc: Joerg Roedel <joro@8bytes.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Kevin Tian <kevin.tian@intel.com>,
	Ashok Raj <ashok.raj@intel.com>,
	Christoph Hellwig <hch@infradead.org>,
	Will Deacon <will@kernel.org>,
	Joao Martins <joao.m.martins@oracle.com>,
	iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCHES 1/2] iommu: Add RCU-protected page free support
Date: Wed, 15 Jun 2022 12:40:40 -0300	[thread overview]
Message-ID: <20220615154040.GA4927@nvidia.com> (raw)
In-Reply-To: <bbada5b7-737f-03dd-7d42-2ebad442a2bb@linux.intel.com>

On Fri, Jun 10, 2022 at 01:37:20PM +0800, Baolu Lu wrote:
> On 2022/6/9 20:49, Jason Gunthorpe wrote:
> > > +void iommu_free_pgtbl_pages(struct iommu_domain *domain,
> > > +			    struct list_head *pages)
> > > +{
> > > +	struct page *page, *next;
> > > +
> > > +	if (!domain->concurrent_traversal) {
> > > +		put_pages_list(pages);
> > > +		return;
> > > +	}
> > > +
> > > +	list_for_each_entry_safe(page, next, pages, lru) {
> > > +		list_del(&page->lru);
> > > +		call_rcu(&page->rcu_head, pgtble_page_free_rcu);
> > > +	}
> > It seems OK, but I wonder if there is benifit to using
> > put_pages_list() from the rcu callback
> 
> The price is that we need to allocate a "struct list_head" and free it
> in the rcu callback as well. Currently the list_head is sitting in the
> stack.

You'd have to use a different struct page layout so that the list_head
was in the struct page and didn't overlap with the rcu_head

Jason

WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe via iommu <iommu@lists.linux-foundation.org>
To: Baolu Lu <baolu.lu@linux.intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>,
	Ashok Raj <ashok.raj@intel.com>,
	Robin Murphy <robin.murphy@arm.com>,
	linux-kernel@vger.kernel.org,
	Christoph Hellwig <hch@infradead.org>,
	iommu@lists.linux-foundation.org,
	Joao Martins <joao.m.martins@oracle.com>,
	Will Deacon <will@kernel.org>
Subject: Re: [RFC PATCHES 1/2] iommu: Add RCU-protected page free support
Date: Wed, 15 Jun 2022 12:40:40 -0300	[thread overview]
Message-ID: <20220615154040.GA4927@nvidia.com> (raw)
In-Reply-To: <bbada5b7-737f-03dd-7d42-2ebad442a2bb@linux.intel.com>

On Fri, Jun 10, 2022 at 01:37:20PM +0800, Baolu Lu wrote:
> On 2022/6/9 20:49, Jason Gunthorpe wrote:
> > > +void iommu_free_pgtbl_pages(struct iommu_domain *domain,
> > > +			    struct list_head *pages)
> > > +{
> > > +	struct page *page, *next;
> > > +
> > > +	if (!domain->concurrent_traversal) {
> > > +		put_pages_list(pages);
> > > +		return;
> > > +	}
> > > +
> > > +	list_for_each_entry_safe(page, next, pages, lru) {
> > > +		list_del(&page->lru);
> > > +		call_rcu(&page->rcu_head, pgtble_page_free_rcu);
> > > +	}
> > It seems OK, but I wonder if there is benifit to using
> > put_pages_list() from the rcu callback
> 
> The price is that we need to allocate a "struct list_head" and free it
> in the rcu callback as well. Currently the list_head is sitting in the
> stack.

You'd have to use a different struct page layout so that the list_head
was in the struct page and didn't overlap with the rcu_head

Jason
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https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply	other threads:[~2022-06-15 15:40 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-09  7:08 [RFC PATCHES 1/2] iommu: Add RCU-protected page free support Lu Baolu
2022-06-09  7:08 ` Lu Baolu
2022-06-09  7:08 ` [RFC PATCHES 2/2] iommu: Replace put_pages_list() with iommu_free_pgtbl_pages() Lu Baolu
2022-06-09  7:08   ` Lu Baolu
2022-06-09 12:49 ` [RFC PATCHES 1/2] iommu: Add RCU-protected page free support Jason Gunthorpe via iommu
2022-06-09 12:49   ` Jason Gunthorpe
2022-06-09 13:19   ` Robin Murphy
2022-06-09 13:19     ` Robin Murphy
2022-06-09 13:32     ` Jason Gunthorpe
2022-06-09 13:32       ` Jason Gunthorpe via iommu
2022-06-10  5:59       ` Baolu Lu
2022-06-10  5:59         ` Baolu Lu
2022-06-10  5:37   ` Baolu Lu
2022-06-10  5:37     ` Baolu Lu
2022-06-15 15:40     ` Jason Gunthorpe [this message]
2022-06-15 15:40       ` Jason Gunthorpe via iommu
2022-06-16  2:27       ` Baolu Lu
2022-06-16  2:27         ` Baolu Lu
2022-06-20  4:04         ` Jason Gunthorpe
2022-06-20  4:04           ` Jason Gunthorpe via iommu
2022-06-09 17:06 ` Raj, Ashok
2022-06-09 17:06   ` Raj, Ashok
2022-06-10  6:05   ` Baolu Lu
2022-06-10  6:05     ` Baolu Lu

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