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Date: Thu, 10 May 2018 18:36:58 -0700 From: Qing Huang <qing.huang@...cle.com> To: Yanjun Zhu <yanjun.zhu@...cle.com>, tariqt@...lanox.com, davem@...emloft.net Cc: netdev@...r.kernel.org, linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] mlx4_core: allocate 4KB ICM chunks 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 <yanjun.zhu@...cle.com> > >> 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 <qing.huang@...cle.com> >>>> Acked-by: Daniel Jurgens <danielj@...lanox.com> >>>> --- >>>> 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); >>>> } >>> >> >
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