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Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1teLX4-0000000GRcH-2s2H; Sat, 01 Feb 2025 22:00:06 +0000 Date: Sat, 1 Feb 2025 22:00:06 +0000 From: Matthew Wilcox To: David Laight Cc: Mateusz Guzik , ebiederm@xmission.com, oleg@redhat.com, brauner@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 6/6] pid: drop irq disablement around pidmap_lock Message-ID: References: <20250201163106.28912-1-mjguzik@gmail.com> <20250201163106.28912-7-mjguzik@gmail.com> <20250201181933.07a3e7e2@pumpkin> <20250201215105.55c0319a@pumpkin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250201215105.55c0319a@pumpkin> X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C386A180009 X-Stat-Signature: w7dw8z53dwccfesok9k8cnfrq8ck6a88 X-Rspam-User: X-HE-Tag: 1738447214-303404 X-HE-Meta: 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 v1MGZNVa x4A2ltRnMInSWjUn7ODZ1THUoolRQMjWNvE0OLDCUmYiigVP6XtB/378ZqdVXrlLo4mzsfj0BfqT9IpZQnAYdkLRwVySq5XUaFRFAwKHOUVE77/UVKhF5AzQRGjM0i9A+HZQ0kIkseCTQ42U5W1joXHkkK2j/zNutNgXSQV8Fuy2itsq23VCmDWDPW7/eT7AcTNKSVnS9FqbuoRiyGpV/tVq3y5ibZhCk9KaAGF0ZerrovVZELgyMPg+uAa18vrGr21EujcbZr7tIIzIJfkgs3Bl0T2M8PNLfycGogPkx/sWvlXYa06laZenJfl7KwS5FF38lAGSmxnPQx2JlWnr3+I47oEDG7/Oex9MA 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, Feb 01, 2025 at 09:51:05PM +0000, David Laight wrote: > I'm not sure what you mean. > Disabling interrupts isn't as cheap as it ought to be, but probably isn't > that bad. Time it. You'll see. > > So while this is indeed a tradeoff, as I understand the sane default > > is to *not* disable interrupts unless necessary. > > I bet to differ. You're wrong. It is utterly standard to take spinlocks without disabling IRQs. We do it all over the kernel. If you think that needs to change, then make your case, don't throw a driveby review. And I don't mean by arguing. Make a change, measure the difference.