On 3/22/15 4:23 PM, David Miller wrote:
I don't even know which version of memcpy ends up being used on M7.
Some of them do things like use VIS. I can follow some regular sparc
asm, there's no way I'm even *looking* at that. Is it really ok to use
VIS registers in random contexts?
Yes, using VIS how we do is alright, and in fact I did an audit of
this about 1 year ago. This is another one of those "if this is
wrong, so much stuff would break"
The only thing funny some of these routines do is fetch 2 64-byte
blocks of data ahead in the inner loops, but that should be fine
right?
On the M7 we'll use the Niagara-4 memcpy.
Hmmm... I'll run this silly sparc kernel memmove through the glibc
testsuite and see if it barfs.
I don't know if you caught Bob's message; he has a hack to bypass memcpy
and memmove in mm/slab.c use a for loop to move entries. With the hack
he is not seeing the problem.
This is the hack:
+static void move_entries(void *dest, void *src, int nr)
+{
+ unsigned long *dp = dest;
+ unsigned long *sp = src;
+
+ for (; nr; nr--, dp++, sp++)
+ *dp = *sp;
+}
+
and then replace the mempy and memmove calls in transfer_objects,
cache_flusharray and drain_array to use move_entries.
I just put it on 4.0.0-rc4 and ditto -- problem goes away, so it clearly
suggests the memcpy or memmove are the root cause.
David
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