Messages in this thread | | | Date | Mon, 8 Jun 2020 16:39:02 +0530 | From | afzal mohammed <> | Subject | Re: ARM: vmsplit 4g/4g |
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Hi,
[ my previous mail did not make into linux-arm-kernel mailing list, got a mail saying it has a suspicious header and that it is waiting moderator approval ]
On Sun, Jun 07, 2020 at 05:11:16PM +0100, Russell King - ARM Linux admin wrote: > On Sun, Jun 07, 2020 at 06:29:32PM +0530, afzal mohammed wrote:
> > get_user_pages_fast() followed by kmap_atomic() & then memcpy() seems > > to work in principle for user copy. > > Have you done any performance evaluation of the changes yet? I think > it would be a good idea to keep that in the picture. If there's any > significant regression, then that will need addressing.
Not yet. Yes, i will do the performance evaluation.
i am also worried about the impact on performance as these [ get_user_pages() or friends, kmap_atomic() ] are additionally invoked in the copy_{from,to}_user() path now.
Note that this was done on a topic branch for user copy. Changes for kernel static mapping to vmalloc has not been merged with these. Also having kernel lowmem w/ a separate asid & switching at kernel entry/exit b/n user & kernel lowmem by changing ttbr0 is yet to be done. Quite a few things remaining to be done to achieve vmsplit 4g/4g
Regards afzal
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