[lkml]   [2009]   [Jun]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFC PATCH v2 03/19] vbus: add connection-client helper infrastructure
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.

 \ /
  Last update: 2009-06-04 20:29    [W:0.072 / U:1.424 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site