[DragonFlyBSD - Bug #3269] (New) Is double-buffer'd buf still required by HAMMER2 ?

[bugtracker-admin at leaf.dragonflybsd.org]

Issue #3269 has been reported by tkusumi.

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Bug #3269: Is double-buffer'd buf still required by HAMMER2 ?
http://bugs.dragonflybsd.org/issues/3269

* Author: tkusumi
* Status: New
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
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This isn't a bug report.
HAMMER2 uses double-buffer'd buf in fs and devvp vnode, which forces strategy routine to memcpy data.

It first appeared in the following commit in 2013, but
"because device buffers can now wind up being a different size"
was changed later on to always use 64KiB, so this no longer applies.

What happens if HAMMER2 uses single-buffer'd buf (like any other non cow fs) in the current code ?


> commit 355d67fcd81e0a7b17007d691bb00bdd151f3d28
> Author: Matthew Dillon <dillon at apollo.backplane.com>
> Date:   Wed Sep 18 19:56:07 2013 -0700
> 
> <snip>
>       My work involved changing the H2 I/O infrastructure to always double-buffer
>       (i.e. logical buffers vs device buffers) because device buffers can now
>       wind up being a different size than the related logical buffers.



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