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([2601:647:4700:9b2:b484:b377:b015:2fad]) by smtp.gmail.com with ESMTPSA id z12sm17727361pfg.123.2020.11.30.11.51.23 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 30 Nov 2020 11:51:24 -0800 (PST) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.120.23.2.4\)) Subject: Re: [RFC PATCH 12/13] fs/userfaultfd: kmem-cache for wait-queue objects From: Nadav Amit In-Reply-To: <20201129004548.1619714-13-namit@vmware.com> Date: Mon, 30 Nov 2020 11:51:22 -0800 Cc: Jens Axboe , Andrea Arcangeli , Peter Xu , Alexander Viro , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Content-Transfer-Encoding: quoted-printable Message-Id: References: <20201129004548.1619714-1-namit@vmware.com> <20201129004548.1619714-13-namit@vmware.com> To: linux-fsdevel@vger.kernel.org X-Mailer: Apple Mail (2.3608.120.23.2.4) 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: > On Nov 28, 2020, at 4:45 PM, Nadav Amit wrote: >=20 > From: Nadav Amit >=20 > Allocating work-queue objects on the stack has usually negative > performance side-effects. First, it is hard to ensure alignment to > cache-lines without increasing the stack size. Second, it might cause > false sharing. Third, it is more likely to encounter TLB misses as > objects are more likely reside on different pages. >=20 > Allocate userfaultfd wait-queue objects on the heap using kmem-cache = for > better performance. Err=E2=80=A6 The wait-queue objects are still on the stack in some cases = that I missed. Will fix.=