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bug#15578: Parameter -d or --direct to open files with flag O_DIRECT?
From: |
Pádraig Brady |
Subject: |
bug#15578: Parameter -d or --direct to open files with flag O_DIRECT? |
Date: |
Thu, 10 Oct 2013 09:09:03 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 |
On 10/10/2013 05:49 AM, Kyle Sallee wrote:
> Please forgive the inconvenience.
> Attaching a gzipped patch file
> ensures the integrity of patch file content.
> I should have presented only the idea
> rather than a patch for the implementation.
>
> I concur dd is already suited to the task.
>
> Please consider
>
> | sed 's/^/if=/' | xargs -r --max-lines=1 dd iflag=direct # in contrast
> with
> | xargs -r --max-lines=4096 cat -d --
>
> Invoking dd 466059 times costs only a slight performance decrease
> as compared with invoking cat 114 times.
> However, this example probably represents rare usage for cat.
>
> Thanks for granting the time and consideration.
Fair point, but still not worth adding to cat(1)
since it's not special in this regard.
Something like this might be more appropriate:
https://github.com/Feh/nocache
Note that doesn't avoid the page cache completely,
and so may be more performant/portable than O_DIRECT.
(dd has this functionality too as described at 'nocache' at:
http://www.gnu.org/software/coreutils/manual/html_node/dd-invocation.html)
cheers,
Pádraig.