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b=T2p0ReId1lbEsFY2DvU/gRohnt8QhyaJ72wS+PSJfzZMB5VFH0JTxi5XcP9d1ZNYc Ef3Hb9Otl0xKCVY08zNMLDo+3zFnK77RWzjFFuV1TNoBKNNEZS5KxfBdB6Ee6pU8JN JdZgD7rQqnLFzoDn0ydqYxhbTyZHAZCcK0OuxR4aS6kif7Vhbz3zFrlDtgzRmSqtsj pph+k+TCZvbzCH5d2hsTB77/MYcGQatq2iq3KS/75MsiG3Wv+0wNTlEelXdElQ03zN dTCxJPEswb1NeCX/DaRnUmCBQKCmKL78bqPFUJCV1t9D8lHc/2+TPw4JH6gtIN/0Ii YD/GqbaYBY9vw== From: Christian Brauner To: Mateusz Guzik Cc: Christian Brauner , linux-kernel@vger.kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, willy@infradead.org, oleg@redhat.com Subject: Re: [PATCH v3 0/2] further damage-control lack of clone scalability Date: Mon, 19 Jan 2026 12:09:10 +0100 Message-ID: <20260119-wohlmeinend-hebamme-1a9c418f3e8d@brauner> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20251206131955.780557-1-mjguzik@gmail.com> References: <20251206131955.780557-1-mjguzik@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" X-Developer-Signature: v=1; a=openpgp-sha256; l=1350; i=brauner@kernel.org; h=from:subject:message-id; bh=GmLMDLqG/ZC6pHQoQ4uFJi6AJiGopiYZNwHKuIrSntM=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWTmCdw2ddu3JWS9yJYXNyd8DJOaG65et0d6+qu+PyaiW 19KPuDU7ihlYRDjYpAVU2RxaDcJl1vOU7HZKFMDZg4rE8gQBi5OAZjI9QRGhr8ykWfrvq1XvPrO auf2E8tjHE5POmvONOVJIW/1hv63b60ZGX4J3Jmz/1vIjAf6u95qda98FrV7/je9A0eEFrTNCW+ r3coDAA== X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: sm6fyyu1jwdxxqbwsibkwinjoa17aft1 X-Rspamd-Queue-Id: AA4DA40004 X-Rspamd-Server: rspam04 X-HE-Tag: 1768820961-384255 X-HE-Meta: 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 dJxN1hn9 wpNis8dYX3/pZKDZZZV+COe89jWk9byMaqnb8lmglIPfkV09dBl+ag7CFeHmP3ls8pg5pPdrMwAWZo/bKqdSE0CA44prJTJwDn9iwAsyrk0rxyV/8SpbOzvg7kMNZc9cZ+Lvq40C4QQW29M9Ci4yPBDZJwZNb6aX+hB3QhylCSNqkKFeptkfoeX3qQyejlb6bzk+mLrU0kBYft/RAB/9O80d5fVHrUsHNlKV+wN5xFH41bIdUQvTohz+Qc39FXLQ7Zeq/f1hgCnlw6zvk11tDngGWJAYMMeL2w4uj X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 Sat, 06 Dec 2025 14:19:53 +0100, Mateusz Guzik wrote: > When spawning and killing threads in separate processes in parallel the > primary bottleneck on the stock kernel is pidmap_lock, largely because > of a back-to-back acquire in the common case. > > Benchmark code at the end. > > With this patchset alloc_pid() only takes the lock once and consequently > alleviates the problem. While scalability improves, the lock remains the > primary bottleneck by a large margin. > > [...] Applied to the kernel-7.0.misc branch of the vfs/vfs.git tree. Patches in the kernel-7.0.misc branch should appear in linux-next soon. Please report any outstanding bugs that were missed during review in a new review to the original patch series allowing us to drop it. It's encouraged to provide Acked-bys and Reviewed-bys even though the patch has now been applied. If possible patch trailers will be updated. Note that commit hashes shown below are subject to change due to rebase, trailer updates or similar. If in doubt, please check the listed branch. tree: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git branch: kernel-7.0.misc [1/2] ns: pad refcount https://git.kernel.org/vfs/vfs/c/0832219c84f2 [2/2] pid: only take pidmap_lock once on alloc https://git.kernel.org/vfs/vfs/c/fb374f0d6fc6