On Sat, Oct 10, 2020 at 10:20:34AM +0800, Coly Li wrote:
On 2020/10/10 03:50, ira.weiny@intel.com wrote:
From: Ira Weiny ira.weiny@intel.com
These kmap() calls are localized to a single thread. To avoid the over head of global PKRS updates use the new kmap_thread() call.
Hi Ira,
There were a number of options considered.
- Attempt to change all the thread local kmap() calls to kmap_atomic()
- Introduce a flags parameter to kmap() to indicate if the mapping
should be global or not 3) Change ~20-30 call sites to 'kmap_global()' to indicate that they require a global mapping of the pages 4) Change ~209 call sites to 'kmap_thread()' to indicate that the mapping is to be used within that thread of execution only
I copied the above information from patch 00/58 to this message. The idea behind kmap_thread() is fine to me, but as you said the new api is very easy to be missed in new code (even for me). I would like to be supportive to option 2) introduce a flag to kmap(), then we won't forget the new thread-localized kmap method, and people won't ask why a _thread() function is called but no kthread created.
Thanks for the feedback.
I'm going to hold off making any changes until others weigh in. FWIW, I kind of like option 2 as well. But there is already kmap_atomic() so it seemed like kmap_XXXX() was more in line with the current API.
Thanks, Ira
Thanks.
Coly Li