Re: [PATCH v2] mm/hmm/test: use xa_for_each_range instead of looping

From: Jason Gunthorpe <jgg@ziepe.ca>
To: Ralph Campbell <rcampbell@nvidia.com>
Cc: linux-rdma@vger.kernel.org, linux-mm@kvack.org,
	linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org,
	Jerome Glisse <jglisse@redhat.com>,
	John Hubbard <jhubbard@nvidia.com>,
	Christoph Hellwig <hch@lst.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Shuah Khan <shuah@kernel.org>
Subject: Re: [PATCH v2] mm/hmm/test: use xa_for_each_range instead of looping
Date: Tue, 19 May 2020 16:50:40 -0300	[thread overview]
Message-ID: <20200519195040.GA29444@ziepe.ca> (raw)
In-Reply-To: <20200516010424.2013-1-rcampbell@nvidia.com>

On Fri, May 15, 2020 at 06:04:24PM -0700, Ralph Campbell wrote:
> The test driver uses an xa_array to store virtual to physical address
> translations for a simulated hardware device. The MMU notifier
> invalidation callback is used to keep the table consistent with the CPU
> page table and is frequently called only for a page or two. However, if
> the test process exits unexpectedly or is killed, the range can be
> [0..ULONG_MAX] in which case calling xa_erase() for every possible PFN
> results in CPU timeouts.
> Use xa_for_each_range() to efficiently erase entries in the range.
> 
> Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
> ---
> 
> This patch is based on Jason Gunthorpe's hmm tree and should be folded
> into the ("mm/hmm/test: add selftest driver for HMM") patch once this
> patch is reviewed, etc.
> 
> v1 -> v2:
> Use xa_for_each_range() instead of special casing [0..ULONG_MAX].
> 
>  lib/test_hmm.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

I squashed this in

Thanks,
Jason