Messages in this thread | | | Date | Tue, 15 May 2007 22:29:12 -0700 | From | Andrew Morton <> | Subject | Re: Pagecache zeroing: zero_user_segment, zero_user_segments and zero_user |
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On Wed, 16 May 2007 14:52:05 +1000 Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> Christoph Lameter wrote: > > On Tue, 15 May 2007, Andrew Morton wrote: > > > > > >>> The functions above default to KM_USER0 which is also always used when > >>> zero_user_page was called except in one single case. We open code that > >>> single case to draw attention to the spot. > >>> > >> > >>Dunno. fwiw, we decided to _not_ embed KM_USER0 in the callee: we have had > >>some pretty ghastly bugs in the past due to misuse of kmap slots so the > >>idea was to shove the decision into the caller's face, make them think > >>about what they're doing > > > > > > On the other hand non highmem platforms are burdened with always repeating > > the same KM_USER0 in every function call. Isnt it enough to know that > > standard functions use KM_USER0 for their operations? > > Couldn't that be filtered out inline?
It is - there is no runtime overhead for non-highmem machines.
The problem nowadays is all the developers who don't need, have, compile for or test on highmem machines.
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