linux-kernel - Re: [PATCH v2 0/4] Update memcpy, memset etc. for M7/M8 architectures

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Message-Id: <20170810.143835.350138228946748074.davem@davemloft.net>
Date:   Thu, 10 Aug 2017 14:38:35 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     babu.moger@...cle.com
Cc:     sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/4] Update memcpy, memset etc. for M7/M8
 architectures

From: Babu Moger <babu.moger@...cle.com>
Date: Mon,  7 Aug 2017 17:52:48 -0600

> This series of patches updates the memcpy, memset, copy_to_user,
> copy_from_user etc for SPARC M7/M8 architecture.

This doesn't build, you cannot assume the existence of "%ncc", it is a
recent addition.

Furthermore there is no need to ever use %ncc in v9 targetted code
anyways.

I'll fix that up, but this was a really disappointing build failure
to hit.

Meanwhile, two questions:

1) Is this also faster on T4 as well?  If it is, we can just get rid
   of the T4 routines and use this on those chips as well.

2) There has been a lot of discussion and consideration put into how
   a memcpy/memset routine might be really great for the local cpu
   but overall pessimize performance for other cpus either locally
   on the same core (contention for physical resources such as
   ports to the store buffer and/or L3 cache) or on other cores.

   Has any such study been done into these issues wrt. this new code?