Subject: Re: port-arm/36513: Pre-cache load length exceeds source memory area in memcpy
To: Steve Woodford <firstname.lastname@example.org>
From: Masao Uebayashi <email@example.com>
Date: 06/20/2007 17:49:06
I'm not Doshita-san, but it was me who translated with confusion, so...
> > Pre-cache load length exceeds source memory area in memcpy.
> > Unrelated area is written back to memory, which causes
> > some troubles.
> Can you elaborate on the "some troubles" part? The source cacheline will
> not be marked dirty by pld, assuming it was already clean or not
> resident in the cache to begin with, so a write-back will not occur.
"Write-back" was wrong. This is all about read (cache fill).
> The only case I can think of where this *may* be an issue would be
> copying from a cacheable memory region which is shared with a
> DMA-capable device...
The place he had problem was a memcpy() in m_dup(9). The memcpy() does
its job correctly, but something slow happens there and the system loses
lots of packets. We guess it's kind of exception, but have not figured out yet.