Messages in this thread | | | Date | Thu, 04 Jun 2009 21:24:33 +0300 | From | Avi Kivity <> | Subject | Re: [RFC PATCH v2 03/19] vbus: add connection-client helper infrastructure |
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Gregory Haskins wrote:
>> BTW, why did you decide to use get_user_pages? >> Would switch_mm + copy_to_user work as well >> avoiding page walk if all pages are present? >> >> > > Well, basic c_t_u() won't work because its likely not "current" if you > are updating the ring from some other task, but I think you have already > figured that out based on the switch_mm suggestion. The simple truth is > I was not familiar with switch_mm at the time I wrote this (nor am I > now). If this is a superior method that allows you to acquire > c_t_u(some_other_ctx) like behavior, I see no problem in changing. I > will look into this, and thanks for the suggestion! >
copy_to_user() is significantly faster than get_user_pages() + kmap() + memcmp() (or their variants).
-- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.
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