Re: [PATCH 0/3 v3] dcache: make it more scalable on large system

[Waiman Long]

On 05/29/2013 12:56 PM, Andi Kleen wrote:
> On Wed, May 29, 2013 at 12:18:09PM -0400, Simo Sorce wrote:
> > To be honest a workload base on /etc/passwd or /etc/group is completely
> > artificial, in actual usage, if you really have  such access you use
> > nscd or sssd with their shared memory caches to completely remove most
> > of the file access.
> I don't fully agree at this point. A lot of things can be tuned away,
> but in practice we want things to perform well out of the box without
> needing all kinds of magic tuning that only
>
> Also this is just normal file access, nothing special about it.
> It simply has to scale. For all kinds of workloads.
>
> And it does, just d_path messes it up.

Just for clarification, the AIM7 workload is not affected by the current 
d_path() code, they are speed-limited by the lock contention in the 
dcache reference counting code. However, both the d_path() change and  
the dentry reference counting change are needed to to eliminate the 
overhead introduced by the use of the perf-record command.

Regards,
Longman
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