netdev - Re: [PATCH v3 -next 11/15] sunrpc: use vfs_pressure

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Message-ID: <5bcb9ace-de01-e597-92a2-22013aa695ba@huawei.com>
Date: Thu, 19 Dec 2024 18:17:36 +0800
From: yukaixiong <yukaixiong@...wei.com>
To: NeilBrown <neilb@...e.de>, Jeff Layton <jlayton@...nel.org>
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Subject: Re: [PATCH v3 -next 11/15] sunrpc: use vfs_pressure_ratio() helper



On 2024/10/11 5:43, NeilBrown wrote:
> On Fri, 11 Oct 2024, Jeff Layton wrote:
>> On Thu, 2024-10-10 at 23:22 +0800, Kaixiong Yu wrote:
>>> Use vfs_pressure_ratio() to simplify code.
>>>
>>> Signed-off-by: Kaixiong Yu <yukaixiong@...wei.com>
>>> Reviewed-by: Kees Cook <kees@...nel.org>
>>> Acked-by: Anna Schumaker <anna.schumaker@...cle.com>
>>> ---
>>>   net/sunrpc/auth.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c
>>> index 04534ea537c8..3d2b51d7e934 100644
>>> --- a/net/sunrpc/auth.c
>>> +++ b/net/sunrpc/auth.c
>>> @@ -489,7 +489,7 @@ static unsigned long
>>>   rpcauth_cache_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
>>>   
>>>   {
>>> -	return number_cred_unused * sysctl_vfs_cache_pressure / 100;
>>> +	return vfs_pressure_ratio(number_cred_unused);
>>>   }
>>>   
>>>   static void
>> Acked-by: Jeff Layton <jlayton@...nel.org>
>>
> I realise this is a bit of a tangent, and I'm not objecting to this
> patch, but I wonder what the justification is for using
> vfs_cache_pressure here.  The sysctl is documented as
>
>     This percentage value controls the tendency of the kernel to reclaim
>     the memory which is used for caching of directory and inode objects.
>
> So it can sensibly be used for dentries and inode, and for anything
> directly related like the nfs access cache (which is attached to inodes)
> and the nfs xattr cache.
>
> But the sunrpc cred cache scales with the number of active users, not
> the number of inodes/dentries.
>
> So I think this should simply "return number_cred_unused;".
>
> What do others think?
>
> NeilBrown
>
> .

Thank you, I will receive your advice.