Re: [PATCH/RFC] MM slub: add a sysfs entry to show the calculated number of fallback slabs

[David Rientjes <rientjes@google.com>]

On Fri, 12 Nov 2010, Richard Kennedy wrote:

> Add a slub sysfs entry to show the calculated number of fallback slabs.
> 
> Using the information already available it is straightforward to
> calculate the number of fallback & full size slabs. We can then track
> which slabs are particularly effected by memory fragmentation and how
> long they take to recover. 
> 
> There is no change to the mainline code, the calculation is only
> performed on request, and the value is available without having to
> enable CONFIG_SLUB_STATS.  
> 

I don't see why this information is generally useful unless debugging an 
issue where statistics are already needed such as ALLOC_SLOWPATH and 
ALLOC_SLAB, so it CONFIG_SLUB_STATS can be enabled to also track 
ORDER_FALLBACK.  All stats can be cleared by writing a '0' to its sysfs 
stats file so you can collect statistics for various workloads without 
rebooting (after doing a forced shrink, for example).

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