From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ira Weiny Date: Sun, 11 Oct 2020 22:28:18 -0700 Subject: [Intel-wired-lan] [PATCH RFC PKS/PMEM 48/58] drivers/md: Utilize new kmap_thread() In-Reply-To: References: <20201009195033.3208459-1-ira.weiny@intel.com> <20201009195033.3208459-49-ira.weiny@intel.com> Message-ID: <20201012052817.GZ2046448@iweiny-DESK2.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: intel-wired-lan@osuosl.org List-ID: On Sat, Oct 10, 2020 at 10:20:34AM +0800, Coly Li wrote: > On 2020/10/10 03:50, ira.weiny at intel.com wrote: > > From: Ira Weiny > > > > 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. > > 1) Attempt to change all the thread local kmap() calls to kmap_atomic() > 2) 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 >