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Re: better buffer size for copy

From: Robert Latham
Subject: Re: better buffer size for copy
Date: Fri, 18 Nov 2005 16:27:54 -0600
User-agent: Mutt/1.5.9i

(README says to ping if there's not been an ack of a patch after two
weeks.  here i go)

This patch to today's (18 Nov 2005) coreutils CVS makes copy.c
consider both the source and destination blocksize when computing
buf_size.  With this patch, src/copy.c will use the LCM of the soruce
and destination block sizes.  As Paul suggested, I used the buffer_lcm
routine from diffutils. 

For what it's worth, this patch does not introduce any regressions
into the coreutils testsuite.

When copying from a remote filesystem with a block size of 4MB to a
filesystem with a 4k blocksize, the copy is *very* slow.  Going from a
filesystem with 4k blocks to a filesystem with 4MB blocks is much
faster.  With this patch, both operations are equally performant.

I went ahead and added a ChangeLog entry as well.  

Thanks.  I'll be more than happy to incorporate any suggestions or


Rob Latham
Mathematics and Computer Science Division    A215 0178 EA2D B059 8CDF
Argonne National Labs, IL USA                B29D F333 664A 4280 315B

Attachment: coreutils-lcm.patch
Description: Text document

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