Re: [PATCH 1/6] NFSD: add the ability to enable use of RWF_DONTCACHE for all IO

Chuck Lever
2025-06-11T13:56:42Z

On 6/11/25 2:57 AM, Christoph Hellwig wrote:
> On Tue, Jun 10, 2025 at 04:57:32PM -0400, Mike Snitzer wrote:
>> Add 'enable-dontcache' to NFSD's debugfs interface so that: Any data
>> read or written by NFSD will either not be cached (thanks to O_DIRECT)
>> or will be removed from the page cache upon completion (DONTCACHE).
>>
>> enable-dontcache is 0 by default. It may be enabled with:
>> echo 1 > /sys/kernel/debug/nfsd/enable-dontcache
>
> Having this as a global debug-only interface feels a bit odd.

This interface is temporary. We expect to implement export options
to control it if that turns out to be necessary.

I don't feel we understand the full performance implications for
most workloads yet, so it seems premature to design and introduce a
permanent administrative interface.

--
Chuck Lever