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Wed, 05 Feb 2020 23:57:19 +0000 Received: from abhmp0018.oracle.com (abhmp0018.oracle.com [141.146.116.24]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 015NvIxZ003008; Wed, 5 Feb 2020 23:57:19 GMT Received: from [192.168.1.206] (/71.63.128.209) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 05 Feb 2020 15:57:18 -0800 Subject: Re: [PATCH v11 4/9] hugetlb: disable region_add file_region coalescing To: Mina Almasry Cc: shuah@kernel.org, rientjes@google.com, shakeelb@google.com, gthelen@google.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, cgroups@vger.kernel.org References: <20200203232248.104733-1-almasrymina@google.com> <20200203232248.104733-4-almasrymina@google.com> From: Mike Kravetz Message-ID: Date: Wed, 5 Feb 2020 15:57:17 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200203232248.104733-4-almasrymina@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9522 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=904 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-2002050185 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9522 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=937 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-2002050185 Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On 2/3/20 3:22 PM, Mina Almasry wrote: > A follow up patch in this series adds hugetlb cgroup uncharge info the > file_region entries in resv->regions. The cgroup uncharge info may > differ for different regions, so they can no longer be coalesced at > region_add time. So, disable region coalescing in region_add in this > patch. > > Behavior change: > > Say a resv_map exists like this [0->1], [2->3], and [5->6]. > > Then a region_chg/add call comes in region_chg/add(f=0, t=5). > > Old code would generate resv->regions: [0->5], [5->6]. > New code would generate resv->regions: [0->1], [1->2], [2->3], [3->5], > [5->6]. > > Special care needs to be taken to handle the resv->adds_in_progress > variable correctly. In the past, only 1 region would be added for every > region_chg and region_add call. But now, each call may add multiple > regions, so we can no longer increment adds_in_progress by 1 in region_chg, > or decrement adds_in_progress by 1 after region_add or region_abort. Instead, > region_chg calls add_reservation_in_range() to count the number of regions > needed and allocates those, and that info is passed to region_add and > region_abort to decrement adds_in_progress correctly. > > We've also modified the assumption that region_add after region_chg > never fails. region_chg now pre-allocates at least 1 region for > region_add. If region_add needs more regions than region_chg has > allocated for it, then it may fail. > > Signed-off-by: Mina Almasry > Reviewed-by: Mike Kravetz This is the same as the previous version. My late comment was that we need to rethink the disabling of region coalescing. This is especially important for private mappings where there will be one region for huge page. I know that you are working on this issue. Please remove my Reviewed-by: when sending out the next version. Thanks, -- Mike Kravetz