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Re: Linux VFS cache hit rate script
On 04/21/2011 04:17 PM, Jake Maul wrote:
> New version of the script uploaded to War Stories, incorporating your
> suggested changes. I have no problem with the GPLv2, so I took your
> wording exactly. :)
>
> http://sourceware.org/systemtap/wiki/WSCacheHitRate
>
> Of course there's still the concern about devname "N/A", but I
> clarified the comment so as to make it obvious where I got that
> assumption from. At least then if does turn out to be incorrect, it
> will be obvious that something other than just this one script needs
> to be fixed.
>
> Jake
Hi Jake,
I traced through vfs.stp and found where the "N/A" is coming from:
function bdevname:string(bdev:long)
{
if (bdev == 0)
return "N/A"
...
}
Whether "N/A" always indicated things are cached I don't know. Need to explore further.
Found a possible reason got the overflow for the associative array; there is an associative array used for caching names in vfs.stp:
global __devnames
function __find_bdevname:string(dev:long, bdev:long)
{
if (dev in __devnames)
return __devnames[dev]
else
return __devnames[dev] = bdevname(bdev)
}
The only way that is going to fill up is if there are a lot of different values for dev.
-Will