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RE: [Xen-devel] [PATCH] Reduce overhead in find_domain_by_id() [0/2]


Earlier this summer I had done some experiments with Iperf and found
that find_domain_id was consuming 7% of cpu while do_grant_table_op was
consuming 10.5%. A quick fix to figure what the upper bound of
performance gain was to remove the hash table lookups in
find_domain_by_id and we saw a 12% improvement in perf receive
The results of these finding were published in our paper at VTDC.
In that paper we also discuss how the inter vm communication by grant
tables was consuming a considerable amount of time and what could be
possibly done to optimize.

I will send the paper is a separate note to you and Renato.

- Padma

-----Original Message-----
From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Keir Fraser
Sent: Wednesday, December 06, 2006 12:44 AM
To: Santos, Jose Renato G; xen-devel@xxxxxxxxxxxxxxxxxxx
Cc: Yoshio Turner; Jose Renato Santos; G John Janakiraman
Subject: Re: [Xen-devel] [PATCH] Reduce overhead in find_domain_by_id()

On 6/12/06 1:35 am, "Santos, Jose Renato G" <joserenato.santos@xxxxxx>

> This is a set of patches to improve performance of
> find_domain_by_id shows up high in profiles for network I/O intensive
> workloads.
> Most of the cost for this function comes from 3 main functions (of
> aproximate equal costs): 1)read_lock(), 2)read_unlock() and
> 3)get_domain().
> These patches replace the lock used for accessing domain_list and
> domain_hash with a lock free RCU scheme. Experiments confirm that the
> cost of find_domain_by_id() is in fact reduced by 2/3.
> The patches apply cleanly to changeset 12732.

Do you have numbers for performance improvement on a macro benchmark?

 -- Keir

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