From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753791AbeEWBl7 (ORCPT ); Tue, 22 May 2018 21:41:59 -0400 Received: from aserp2130.oracle.com ([141.146.126.79]:33522 "EHLO aserp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753578AbeEWBl5 (ORCPT ); Tue, 22 May 2018 21:41:57 -0400 From: Qing Huang Subject: Re: [PATCH v3] mlx4_core: allocate ICM memory in page size chunks To: Tariq Toukan , Eric Dumazet , davem@davemloft.net, haakon.bugge@oracle.com, yanjun.zhu@oracle.com Cc: netdev@vger.kernel.org, linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, gi-oh.kim@profitbricks.com References: <20180517205343.8401-1-qing.huang@oracle.com> <19b7818e-16f6-2349-dc34-245c2f215f6f@oracle.com> <35ba0f14-7b24-96ff-6b2d-610a4b2980c2@mellanox.com> Message-ID: <4b7a4f67-2c08-a60d-81cd-f12db42622ec@oracle.com> Date: Tue, 22 May 2018 18:41:39 -0700 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <35ba0f14-7b24-96ff-6b2d-610a4b2980c2@mellanox.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8901 signatures=668700 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=9 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1805230013 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/22/2018 8:33 AM, Tariq Toukan wrote: > > > On 18/05/2018 12:45 AM, Qing Huang wrote: >> >> >> On 5/17/2018 2:14 PM, Eric Dumazet wrote: >>> On 05/17/2018 01:53 PM, Qing Huang wrote: >>>> When a system is under memory presure (high usage with fragments), >>>> the original 256KB ICM chunk allocations will likely trigger kernel >>>> memory management to enter slow path doing memory compact/migration >>>> ops in order to complete high order memory allocations. >>>> >>>> When that happens, user processes calling uverb APIs may get stuck >>>> for more than 120s easily even though there are a lot of free pages >>>> in smaller chunks available in the system. >>>> >>>> Syslog: >>>> ... >>>> Dec 10 09:04:51 slcc03db02 kernel: [397078.572732] INFO: task >>>> oracle_205573_e:205573 blocked for more than 120 seconds. >>>> ... >>>> >>> NACK on this patch. >>> >>> You have been asked repeatedly to use kvmalloc() >>> >>> This is not a minor suggestion. >>> >>> Take a look >>> athttps://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d8c13f2271ec5178c52fbde072ec7b562651ed9d >>> >> >> Would you please take a look at how table->icm is being used in the >> mlx4 driver? It's a meta data used for individual pointer variable >> referencing, >> not as data frag or in/out buffer. It has no need for contiguous phy. >> memory. >> >> Thanks. >> > > NACK. > > This would cause a degradation when iterating the entries of table->icm. > For example, in mlx4_table_get_range. E.g. int mlx4_table_get_range(struct mlx4_dev *dev, struct mlx4_icm_table *table,                          u32 start, u32 end) {         int inc = MLX4_TABLE_CHUNK_SIZE / table->obj_size;         int err;         u32 i;         for (i = start; i <= end; i += inc) {                 err = mlx4_table_get(dev, table, i);                 if (err)                         goto fail;         }         return 0; ... } E.g. mtt obj is 8 bytes, so a 4KB ICM block would have 512 mtt objects. So you will have to allocate more 512 mtt objects in order to have table->icm pointer to increment by 1 to fetch next pointer value.  So 256K mtt objects are needed in order to traverse table->icm pointer across a page boundary in the call stacks. Considering mlx4_table_get_range() is only used in control path, there is no significant gain by using kvzalloc vs. vzalloc for table->icm. Anyway, if a user makes sure mlx4 driver to be loaded very early and doesn't remove and reload it afterwards, we should have enough (and not wasting) contiguous phy mem for table->icm allocation. I will use kvzalloc to replace vzalloc and send a V4 patch. Thanks, Qing > > Thanks, > Tariq > >>> And you'll understand some people care about this. >>> >>> Strongly. >>> >>> Thanks. >>> >> > -- > To unsubscribe from this list: send the line "unsubscribe linux-rdma" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html