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Tsirkin" , David Hildenbrand , Jason Wang , Dave Hansen , Michal Hocko , Liang Li Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: Re: [RFC v2 PATCH 0/4] speed up page allocation for __GFP_ZERO In-Reply-To: <20201221162519.GA22504@open-light-1.localdomain> References: <20201221162519.GA22504@open-light-1.localdomain> Date: Tue, 22 Dec 2020 12:11:21 -0500 Message-ID: <87wnx9rcjq.fsf@oracle.com> MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9842 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 bulkscore=0 malwarescore=0 phishscore=0 mlxscore=0 adultscore=0 spamscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012220127 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9842 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 lowpriorityscore=0 suspectscore=0 adultscore=0 bulkscore=0 priorityscore=1501 mlxscore=0 clxscore=1011 phishscore=0 mlxlogscore=999 spamscore=0 impostorscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012220127 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: Liang Li writes: > The first version can be found at: https://lkml.org/lkml/2020/4/12/42 > > Zero out the page content usually happens when allocating pages with > the flag of __GFP_ZERO, this is a time consuming operation, it makes > the population of a large vma area very slowly. This patch introduce > a new feature for zero out pages before page allocation, it can help > to speed up page allocation with __GFP_ZERO. kzeropaged appears to escape some of the kernel's resource controls, at least if I'm understanding this right. The heavy part of a page fault is moved out of the faulting task's context so the CPU controller can't throttle it. A task that uses these pages can benefit from clearing done by CPUs that it's not allowed to run on. How can it handle these cases?