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ZWi7rfeq1U+gfe9k4HSv2M6x51Ixyyoos4WIX8B4G6eF5a5Up2CpZp4YyYy/p2WXJTW44txNz22RDg6KoFJr0cvc2koOhPVoEOHbVbwbw5toeo4l/mwLIrzIBovnvFST7utAfjvh4js3i3s0FFz7/9ZdC+9F11/1vwHzenyI1IQDlpVuAXU8vV45/iBzxBn7VXrKZ0VzXcKEFYWWNpwXawlgp6/8ZXmIvRKLzXK+sEArC+5okb1f1x4or92a9AfZ7jAhSyaR7jhsdBqryrc5ytigOMPYHeS5dMhrFTTxfuXHjL8z4r8FTPwnbqib2laK2RO2GQ/c4bE3aKTvGtH2vOdHpWug9RxVWWC/oZlCrQ+MUEfuOodKobF3nKoKRz/WuD/v+wQWXzwCtKJNIltaNTf8APBFwAeIhPiPP X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/19/2024 12:16 PM, Linus Torvalds wrote: > On Thu, 19 Sept 2024 at 00:44, Neeraj Upadhyay wrote: >> >> While we were working on this problem, this refcount scalability issue got >> resolved recently with conditional ref acquisition [3] (however, there are new >> developments in apparmor code which might bring back the refcount problem [4]). > > Honestly, the various security layers should be a whole lot more > careful about their horrid performance issues, and I think that [4] > you point at needs to just be headed off at the pass. > > No more "the security layer is so bad at performance that we have to > introduce new ref mechanisms", please. Let's push back on bad security > layer code instead. > Ok got it. Thanks for your feedback! I had tried using percpu refcount first (in place of kref) in AppArmor. However, that required managing the last reference drop (implemented in [1] and [2]). Mateusz has shared some ideas in his reply to this thread. Maybe that is a workable solution. Will defer to John on this as I have limited understanding of the cred management code. - Neeraj > Linus