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SubjectRe: Read speed
You will need a more recent kernel (probably based on the 3.2 kernel
or later, 3.2 was released a year or so ago) to see the dramatic
improvements in cifs read speeds (with the redesign of the read code
to add more parallelism on i/o to the same file) although RedHat may
have backported some of Jeff's excellent performance improvements to
some of the older distros. See slides 21 through 26 of my
presentation at

Slides 23 and 24 list the cifs performance and functional enhancements
by kernel release. Buffered, sequential read (e.g. file copy from a
server) got much faster in 3.2 kernel, especially to Samba and other
server which support the Unix extensions (due to support for larger
i/o sizes than 64K).

Similarly note that cifs write speed was dramatically improved
starting at kernel version 3.0 (1.5 to 2 years ago) due to the
addition of more async parallelism to the design of the cifs write
code (writing to the server from the cifs client) by making the i/o
sizes larger and allowing more async dispatch of writes (previously to
use a network interface fully you would need to be reading and or
writing to multiple different files simultaneously).

On Mon, Feb 4, 2013 at 7:23 PM, Jeff Blaine <> wrote:
> Hi,
> On a RHEL 6.3 box talking to a Windows 7 Enterprise box,
> I am seeing approximately 1/4th the speed with mount.cifs
> as I am with smbclient 'get'. RHEL 6.3 currently has
> CIFS 1.68.
> After about a half hour of reading forum threads for the
> last few years, it seems this is very well known and has
> been the case for a long time.
> I have tried using CIFSMaxBufSize=61440 with rsize=61140
> at mount-time and it doesn't really buy me much.
> Is there any sort of public-facing summary of the state of
> the read performance issues. I saw no mention of it in the
> BUGS section of the mount.cifs man page or in the README for
> the kernel module.
> Is the cause known?
> Has already been fixed since 1.68 by chance? If so,
> what assembly of pieces will overcome the issue? Should
> I just open a RHEL bug through our support channel and
> get them involved in this effort somehow?
> Any guidance would be welcome at this point.
> Jeff
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