Re: [PATCH] omap4: enable L2 prefetching

["Måns Rullgård" <mans@mansr.com>]

Nishanth Menon <nm@ti.com> writes:

> From: Mans Rullgard <mans@mansr.com>
>
> Enabling L2 prefetching improves performance as shown on Panda
> ES2.1 board with mem test, and it has measurable impact on
> performances. I think we should consider it, even though it damages
> "writes" a bit. (rebased to k.org)
> Usually the prefetch is used at both levels together L1 + L2, however,
> to enable the CP15 prefetch engines, these are under security, and on
> GP devices, we cannot enable it(e.g. on PandaBoard). However, just
> enabling PL310 prefetch seems to provide performance improvement,
> as shown in the data below (from Ubuntu) and would be a great thing
> to pull in.

What this does is enable automatic next line prefetching.  With this
enabled, whenever the PL310 receives a cachable read request, it
automatically prefetches the following cache line as well.  A larger
offset can be programmed in secure mode, but the TI ROM authors
neglected to include this.

Testing with FFmpeg showed a speedup of 10% with this patch in some
cases.

-- 
Måns Rullgård
mans@mansr.com

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