Re: CVS commit: [simonb-wapbl] src/sys/kern

[Jason Thorpe <thorpej%shagadelic.org@localhost>]

On Jul 27, 2008, at 9:04 PM, Greg Oster wrote:

> Module Name:    src
> Committed By:   oster
> Date:           Mon Jul 28 04:04:32 UTC 2008
>
> Modified Files:
>         src/sys/kern [simonb-wapbl]: vfs_wapbl.c
>
> Log Message:
> Turn on WAPBL_DEBUG_SERIALIZE in order to use RW_WRITER locks instead
> of RW_READER locks in wapbl_begin().  Include the following comment as
> well:
>
>         XXX: The original code calls for the use of a RW_READER lock
>         here, but it turns out there are performance issues with high
>         metadata-rate workloads (e.g. multiple simultaneous tar
>         extractions).  For now, we force the lock to be RW_WRITER,
>         since that currently has the best performance characteristics
>         (even for a single tar-file extraction).

Uh, scary.  Has anyone done any analysis of why this is so?


> Approved by: simonb
>
>
> To generate a diff of this commit:
> cvs rdiff -r1.1.2.10 -r1.1.2.11 src/sys/kern/vfs_wapbl.c
>
> Please note that diffs are not public domain; they are subject to the
> copyright notices on the relevant files.

-- thorpej