Bug#628558: Plaease enable FSCACHE_HISTOGRAM

[maximilian attems <max@stro.at>]

On Mon, 30 May 2011, Laurent Bonnaud wrote:

> Package: linux-2.6
> Version: 2.6.39-1
> Severity: wishlist
> 
> 
> Hi,
> 
> in this documentation file:
> 
>   /usr/share/doc/linux-doc-2.6.39/Documentation/filesystems/caching/fscache.txt.gz
> 
> the kernel options
> 
>         CONFIG_FSCACHE_STATS=y
>         CONFIG_FSCACHE_HISTOGRAM=y
> 
> are suggested to check the efficiency of fscache.  However only the
> first one is enabled:
> 
> $ grep CONFIG_FSCACHE /boot/config-2.6.39-1-686-pae 
> CONFIG_FSCACHE=m
> CONFIG_FSCACHE_STATS=y
> # CONFIG_FSCACHE_HISTOGRAM is not set
> # CONFIG_FSCACHE_DEBUG is not set
> # CONFIG_FSCACHE_OBJECT_LIST is not set
> 
> So could you please enable CONFIG_FSCACHE_HISTOGRAM ?

config FSCACHE_HISTOGRAM
        bool "Gather latency information on local caching"
        depends on FSCACHE && PROC_FS
        help
          This option causes latency information to be gathered on local
          caching and exported through file:

                /proc/fs/fscache/histogram

          The generation of this histogram adds a certain amount of overhead to
          execution as there are a number of points at which data is gathered,
          and on a multi-CPU system these may be on cachelines that keep
          bouncing between CPUs.  On the other hand, the histogram may be
          useful for debugging purposes.  Saying 'N' here is recommended.

          See Documentation/filesystems/caching/fscache.txt for more information.

It is also disabled on fedora linux images.

Unless you come up with a real good reason to enable it,
this bug report can be closed.

-- 
maks