Messages in this thread | | | Date | Sat, 16 Nov 2002 13:50:17 -0500 | From | Akira Tsukamoto <> | Subject | Re: [CFT][PATCH] 2.5.47 Athlon/Druon, much faster copy_user function |
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Hi,
On Sat, 16 Nov 2002 19:30:03 +0100 Andi Kleen <ak@suse.de> mentioned: > > The proper way to save it is to use kernel_fpu_begin()
Thanks! I will look into it. This is what I was looking for.
I been running this kernel with my copy for three days, and never had oops, but I was really worried.
> > > Also I'm pretty sure that using movntq (= forcing destination out of > > > cache) is not a good strategy for generic copy_from_user(). It may > > > be a win for the copies in write ( user space -> page cache ), > > > > Yes, that why I included postfetch in the code because movntq does not leave > > them in the L2 cache. > > That looks rather wasteful - first force it out and then trying to get it in > again. I have my doubts on it being a good strategy for speed.
It tried both, use just normal mov or movq <-> use movntq + postfetch, and the later was much much faster, because postfetch needs to read only every 64 bytes.
I will ckeck kernel_fpu_begin() fisrt and if using fpu register is too much overhead than I will remove them.
Akira
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