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Date: Mon, 29 Nov 2010 08:28:05 -0600
From: Bill Kendall <wkendall@sgi.com>
MIME-Version: 1.0
Subject: Re: [PATCH v4 4/9] xfsrestore: mmap dirent names for faster lookups
References: <20101119183837.GA9505@sgi.com>
	<20101123134818.GA31206@infradead.org>
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To: Christoph Hellwig <hch@infradead.org>
Cc: xfs@oss.sgi.com

On 11/23/2010 07:48 AM, Christoph Hellwig wrote:
> On Fri, Nov 19, 2010 at 12:38:37PM -0600, Bill Kendall wrote:
>> Pathname resolution in xfsrestore is about 4x faster if the file
>> containing dirent names ("namreg") is memory mapped.  If xfsrestore is
>> unable to map the file (e.g., due to virtual memory constraints)
>> fallback to the existing seek-and-read approach.
>>
>> The file is mapped after all directory entries have been written to
>> the "namreg" file. If the caller tries to add additional entries after
>> the file has been mapped, it will be unmapped and restore will resort
>> back to seek-and-read lookups.
>
> This looks much simpler indeed.  Is it intentional that the namreg file
> is never unmapped any more?

There are several modules in xfsrestore which map files. None of them
currently contain a destructor/cleanup function for unmapping the files.
It would be a good change to make though.

Bill

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