Re: (subset) [PATCH v5 00/13] NFSD DIRECT and NFS DIRECT

[Chuck Lever <cel@kernel.org>]

On 7/28/25 9:51 AM, Mike Snitzer wrote:
> On Sun, Jul 27, 2025 at 12:16:04PM -0400, Chuck Lever wrote:
>> From: Chuck Lever <chuck.lever@oracle.com>
>>
>> On Thu, 24 Jul 2025 15:30:49 -0400, Mike Snitzer wrote:
>>> Some workloads benefit from NFSD avoiding the page cache, particularly
>>> those with a working set that is significantly larger than available
>>> system memory.  This patchset introduces _optional_ support to
>>> configure the use of O_DIRECT or DONTCACHE for NFSD's READ and WRITE
>>> support.  The NFSD default to use page cache is left unchanged.
>>>
>>> The performance win associated with using NFSD DIRECT was previously
>>> summarized here:
>>> https://lore.kernel.org/linux-nfs/aEslwqa9iMeZjjlV@kernel.org/
>>> This picture offers a nice summary of performance gains:
>>> https://original.art/NFSD_direct_vs_buffered_IO.jpg
>>>
>>> [...]
>>
>> Applied to nfsd-testing, thanks!
>>
>> [01/13] NFSD: filecache: add STATX_DIOALIGN and STATX_DIO_READ_ALIGN support
>>         commit: af157e09634a113da83d8ac5fff541f9e06ad653
> 
>> [05/13] NFSD: filecache: only get DIO alignment attrs if NFSD_IO_DIRECT enabled
>>         commit: af157e09634a113da83d8ac5fff541f9e06ad653
> 
> I noticed you folded these, unfortunately that isn't bisect safe
> unless you pull these fs/nfsd/nfsd.h changes to the front too:
> 
> git diff f76b72e4908c556021d94bdeca86fffce430c791^..a45da44bb6bade1dfef569c792ae2ee6507f4724 -- fs/nfsd/nfsd.h
> 
> diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
> index 1cd0bed57bc2..fe935b4cda53 100644
> --- a/fs/nfsd/nfsd.h
> +++ b/fs/nfsd/nfsd.h
> @@ -153,6 +153,16 @@ static inline void nfsd_debugfs_exit(void) {}
>  
>  extern bool nfsd_disable_splice_read __read_mostly;
>  
> +enum {
> +	NFSD_IO_UNSPECIFIED = 0,
> +	NFSD_IO_BUFFERED,
> +	NFSD_IO_DONTCACHE,
> +	NFSD_IO_DIRECT,
> +};
> +
> +extern u64 nfsd_io_cache_read __read_mostly;
> +extern u64 nfsd_io_cache_write __read_mostly;
> +
>  extern int nfsd_max_blksize;
>  
>  static inline int nfsd_v4client(struct svc_rqst *rq)
> 
>> [02/13] NFSD: pass nfsd_file to nfsd_iter_read()
>>         commit: 63a534c8b18642dc27318e08b77952c4d7f55628
>> [03/13] NFSD: add io_cache_read controls to debugfs interface
>>         commit: f76b72e4908c556021d94bdeca86fffce430c791
>> [04/13] NFSD: add io_cache_write controls to debugfs interface
>>         commit: a45da44bb6bade1dfef569c792ae2ee6507f4724
> 
>> [06/13] NFSD: issue READs using O_DIRECT even if IO is misaligned
>>         commit: 6d80efb3cb6f9817bedfa460e9ddf56a916caf2f
> 
> Thanks!
> Mike

That's what I get for compile-testing first before squashing.


-- 
Chuck Lever