From mboxrd@z Thu Jan 1 00:00:00 1970 From: Qing Huang Subject: Re: [PATCH] mlx4_core: allocate 4KB ICM chunks Date: Thu, 10 May 2018 18:36:58 -0700 Message-ID: References: <20180510233143.7236-1-qing.huang@oracle.com> <6454d5eb-2700-4fe2-fd91-d366112c4674@oracle.com> <4a23dac7-fafe-3b1c-7284-75f3a38f420c@oracle.com> <6768e075-70f5-4de3-a98a-fdffa53e0a2f@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: netdev@vger.kernel.org, linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org To: Yanjun Zhu , tariqt@mellanox.com, davem@davemloft.net Return-path: In-Reply-To: <6768e075-70f5-4de3-a98a-fdffa53e0a2f@oracle.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Thank you for reviewing it! On 5/10/2018 6:23 PM, Yanjun Zhu wrote: > > > > On 2018/5/11 9:15, Qing Huang wrote: >> >> >> >> On 5/10/2018 5:13 PM, Yanjun Zhu wrote: >>> >>> >>> On 2018/5/11 7:31, 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. >>>> ... >>>> >>>> With 4KB ICM chunk size, the above issue is fixed. >>>> >>>> However in order to support 4KB ICM chunk size, we need to fix another >>>> issue in large size kcalloc allocations. >>>> >>>> E.g. >>>> Setting log_num_mtt=30 requires 1G mtt entries. With the 4KB ICM chunk >>>> size, each ICM chunk can only hold 512 mtt entries (8 bytes for >>>> each mtt >>>> entry). So we need a 16MB allocation for a table->icm pointer array to >>>> hold 2M pointers which can easily cause kcalloc to fail. >>>> >>>> The solution is to use vzalloc to replace kcalloc. There is no need >>>> for contiguous memory pages for a driver meta data structure (no need >>> Hi, >>> >>> Replace continuous memory pages with virtual memory, is there any >>> performance loss? >> >> Not really. "table->icm" will be accessed as individual pointer >> variables randomly. Kcalloc > > Sure. Thanks. If "table->icm" will be accessed as individual pointer > variables randomly, the performance loss > caused by discontinuous memory will be very trivial. > > Reviewed-by: Zhu Yanjun > >> also returns a virtual address except its mapped pages are guaranteed >> to be contiguous >> which will provide little advantage over vzalloc for individual >> pointer variable access. >> >> Qing >> >>> >>> Zhu Yanjun >>>> of DMA ops). >>>> >>>> Signed-off-by: Qing Huang >>>> Acked-by: Daniel Jurgens >>>> --- >>>>   drivers/net/ethernet/mellanox/mlx4/icm.c | 14 +++++++------- >>>>   1 file changed, 7 insertions(+), 7 deletions(-) >>>> >>>> diff --git a/drivers/net/ethernet/mellanox/mlx4/icm.c >>>> b/drivers/net/ethernet/mellanox/mlx4/icm.c >>>> index a822f7a..2b17a4b 100644 >>>> --- a/drivers/net/ethernet/mellanox/mlx4/icm.c >>>> +++ b/drivers/net/ethernet/mellanox/mlx4/icm.c >>>> @@ -43,12 +43,12 @@ >>>>   #include "fw.h" >>>>     /* >>>> - * We allocate in as big chunks as we can, up to a maximum of 256 KB >>>> - * per chunk. >>>> + * We allocate in 4KB page size chunks to avoid high order memory >>>> + * allocations in fragmented/high usage memory situation. >>>>    */ >>>>   enum { >>>> -    MLX4_ICM_ALLOC_SIZE    = 1 << 18, >>>> -    MLX4_TABLE_CHUNK_SIZE    = 1 << 18 >>>> +    MLX4_ICM_ALLOC_SIZE    = 1 << 12, >>>> +    MLX4_TABLE_CHUNK_SIZE    = 1 << 12 >>>>   }; >>>>     static void mlx4_free_icm_pages(struct mlx4_dev *dev, struct >>>> mlx4_icm_chunk *chunk) >>>> @@ -400,7 +400,7 @@ int mlx4_init_icm_table(struct mlx4_dev *dev, >>>> struct mlx4_icm_table *table, >>>>       obj_per_chunk = MLX4_TABLE_CHUNK_SIZE / obj_size; >>>>       num_icm = (nobj + obj_per_chunk - 1) / obj_per_chunk; >>>>   -    table->icm      = kcalloc(num_icm, sizeof(*table->icm), >>>> GFP_KERNEL); >>>> +    table->icm      = vzalloc(num_icm * sizeof(*table->icm)); >>>>       if (!table->icm) >>>>           return -ENOMEM; >>>>       table->virt     = virt; >>>> @@ -446,7 +446,7 @@ int mlx4_init_icm_table(struct mlx4_dev *dev, >>>> struct mlx4_icm_table *table, >>>>               mlx4_free_icm(dev, table->icm[i], use_coherent); >>>>           } >>>>   -    kfree(table->icm); >>>> +    vfree(table->icm); >>>>         return -ENOMEM; >>>>   } >>>> @@ -462,5 +462,5 @@ void mlx4_cleanup_icm_table(struct mlx4_dev >>>> *dev, struct mlx4_icm_table *table) >>>>               mlx4_free_icm(dev, table->icm[i], table->coherent); >>>>           } >>>>   -    kfree(table->icm); >>>> +    vfree(table->icm); >>>>   } >>> >> >