Subject: Re: [PATCH V4 0/3] scsi: core: avoid big pre-allocation for sg list

From: Ming Lei <[email-masked]>
Date: Sun, 5 May 2019 09:10:18 +0800

On Sun, Apr 28, 2019 at 03:39:29PM +0800, Ming Lei wrote:
> Hi,
> 
> Since supporting to blk-mq, big pre-allocation for sg list is introduced,
> this way is very unfriendly wrt. memory consumption.
> 
> There were Red Hat internal reports that some scsi_debug based tests
> can't be run any more because of too big pre-allocation.
> 
> Also lpfc users commplained that 1GB+ ram is pre-allocatd for single
> HBA.
> 
> sg_alloc_table_chained() is improved to support variant size of 1st
> pre-allocated SGL in the 1st patch as suggested by Christoph.
> 
> The other two patches try to address this issue by allocating sg list runtime,
> meantime pre-allocating one or two inline sg entries for small IO. This
> ways follows NVMe's approach wrt. sg list allocation.
> 
> V4:
> 	- add parameter to sg_alloc_table_chained()/sg_free_table_chained()
> 	directly, and update current callers
> 
> V3:
> 	- improve sg_alloc_table_chained() to accept variant size of
> 	the 1st pre-allocated SGL
> 	- applies the improved sg API to address the big pre-allocation
> 	issue
> 
> V2:
> 	- move inline sg table initializetion into one helper
> 	- introduce new helper for getting inline sg
> 	- comment log fix
> 
> 
> Ming Lei (3):
>   lib/sg_pool.c: improve APIs for allocating sg pool
>   scsi: core: avoid to pre-allocate big chunk for protection meta data
>   scsi: core: avoid to pre-allocate big chunk for sg list
> 
>  drivers/nvme/host/fc.c            |  7 ++++---
>  drivers/nvme/host/rdma.c          |  7 ++++---
>  drivers/nvme/target/loop.c        |  4 ++--
>  drivers/scsi/scsi_lib.c           | 31 ++++++++++++++++++++++---------
>  include/linux/scatterlist.h       | 11 +++++++----
>  lib/scatterlist.c                 | 36 +++++++++++++++++++++++-------------
>  lib/sg_pool.c                     | 37 +++++++++++++++++++++++++++----------
>  net/sunrpc/xprtrdma/svc_rdma_rw.c |  5 +++--
>  8 files changed, 92 insertions(+), 46 deletions(-)
> 
> Cc: Christoph Hellwig <[email-masked]>
> Cc: Bart Van Assche <[email-masked]>
> Cc: Ewan D. Milne <[email-masked]>
> Cc: Hannes Reinecke <[email-masked]>
> Cc: Sagi Grimberg <[email-masked]>
> Cc: Chuck Lever <[email-masked]>
> Cc: [email-masked]
> Cc: [email-masked]

Hi Martin,

Could you consider to merge this patchset to 5.2 if you are fine?

Thanks,
Ming