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charset=us-ascii Content-Disposition: inline In-Reply-To: <5d621db9-23d4-e140-45eb-d7fca2093d2b@intel.com> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-aio@kvack.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, Peter Zijlstra , linux-mmc@vger.kernel.org, Dave Hansen , dri-devel@lists.freedesktop.org, linux-mm@kvack.org, target-devel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-kselftest@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, Ira Weiny , Thomas Gleixner , drbd-dev@lists.linbit.com, devel@driverdev.osuosl.org, linux-cifs@vger.kernel.org, linux-nilfs@vger.kernel.org, linux-scsi@vger.kernel.org, linux-nvdimm@lists.01.org, linux-rdma@vger.kernel.org, x86@kernel.org, amd-gfx@lists.freedesktop.org, linux-afs@lists.infradead.org, Eric Biggers , Ingo Molnar , intel-wired-lan@lists.osuosl.org, kexec@lists.infradead.org, xen-devel@lists.xenproject.org, linux-ext4@vger.kernel.org, bpf@vger.kernel.org, Dan Williams , Fenghua Yu , intel-gfx@lists.freedesktop.org, ecryptfs@vger.kernel.org, linux-um@lists.infradead.org, reiserfs-devel@vger.kernel.org, linux-block@vger.kernel.org, linux-bcache@vger.kernel.org, Borislav Petkov , Andy Lutomirski , Jaegeuk Kim , ceph-devel@vger.kernel.org, io-uring@vger.kernel.org, linux-cachefs@redhat.com, linux-nfs@vger.kernel.org, linux-ntfs-dev@lists.sourceforge.net, netdev@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, samba-technical@lists.samba.org, linux-kernel@vger.kernel.org, cluster-devel@redhat.com, linux-fsdevel@vger.kernel.org, Andrew Morton , linux-erofs@lists.ozlabs.org, linux-btrfs@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Mon, Oct 12, 2020 at 09:28:29AM -0700, Dave Hansen wrote: > kmap_atomic() is always preferred over kmap()/kmap_thread(). > kmap_atomic() is _much_ more lightweight since its TLB invalidation is > always CPU-local and never broadcast. > > So, basically, unless you *must* sleep while the mapping is in place, > kmap_atomic() is preferred. But kmap_atomic() disables preemption, so the _ideal_ interface would map it only locally, then on preemption make it global. I don't even know if that _can_ be done. But this email makes it seem like kmap_atomic() has no downsides.