git: 02ec31bdf60f - main - cache: add back target entry on rename

[Kubilay Kocak]

On 24/01/2021 7:22 am, Mateusz Guzik wrote:
> The sysctl at hand is temporary in case someone reports trouble --
> then they can flip it. I don't expect it to survive more than a month.
> 
> On 1/23/21, Oliver Pinter <oliver.pntr at gmail.com> wrote:
>> On Saturday, January 23, 2021, Mateusz Guzik <mjg at freebsd.org> wrote:
>>
>>> The branch main has been updated by mjg:
>>>
>>> URL: https://cgit.FreeBSD.org/src/commit/?id=
>>> 02ec31bdf60fa3a8530544cb3c8c4ec1df6cde0d
>>>
>>> commit 02ec31bdf60fa3a8530544cb3c8c4ec1df6cde0d
>>> Author:     Mateusz Guzik <mjg at FreeBSD.org>
>>> AuthorDate: 2021-01-23 17:21:42 +0000
>>> Commit:     Mateusz Guzik <mjg at FreeBSD.org>
>>> CommitDate: 2021-01-23 18:10:16 +0000
>>>
>>>      cache: add back target entry on rename
>>> ---
>>>   sys/kern/vfs_cache.c | 19 +++++++++++++++++++
>>>   1 file changed, 19 insertions(+)
>>>
>>> diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c
>>> index 770c8ebf061b..03bafc75acaa 100644
>>> --- a/sys/kern/vfs_cache.c
>>> +++ b/sys/kern/vfs_cache.c
>>> @@ -367,6 +367,10 @@ static bool __read_frequently cache_fast_revlookup =
>>> true;
>>>   SYSCTL_BOOL(_vfs, OID_AUTO, cache_fast_revlookup, CTLFLAG_RW,
>>>       &cache_fast_revlookup, 0, "");
>>>
>>> +static bool __read_mostly cache_rename_add = true;
>>> +SYSCTL_BOOL(_vfs, OID_AUTO, cache_rename_add, CTLFLAG_RW,
>>> +    &cache_rename_add, 0, "");
>>
>>
>>   It would be really if the description were filled with proper info.
>>
>> +
>>>   static u_int __exclusive_cache_line neg_cycle;
>>>
>>>   #define ncneghash      3
>>> @@ -2731,6 +2735,21 @@ cache_vop_rename(struct vnode *fdvp, struct vnode
>>> *fvp, struct vnode *tdvp,
>>>          } else {
>>>                  cache_remove_cnp(tdvp, tcnp);
>>>          }
>>> +
>>> +       /*
>>> +        * TODO
>>> +        *
>>> +        * Historically renaming was always purging all revelang entries,
>>> +        * but that's quite wasteful. In particular turns out that in
>>> many
>>> cases
>>> +        * the target file is immediately accessed after rename, inducing
>>> a cache
>>> +        * miss.
>>> +        *
>>> +        * Recode this to reduce relocking and reuse the existing entry
>>> (if any)
>>> +        * instead of just removing it above and allocating a new one
>>> here.
>>> +        */
>>> +       if (cache_rename_add) {
>>> +               cache_enter(tdvp, fvp, tcnp);
>>> +       }
>>>   }
>>>
>>>   void
>>> _______________________________________________
>>> dev-commits-src-all at freebsd.org mailing list
>>> https://lists.freebsd.org/mailman/listinfo/dev-commits-src-all
>>> To unsubscribe, send any mail to "dev-commits-src-all-
>>> unsubscribe at freebsd.org"
>>>
>>
> 
> 

Could we:

description: "QA/Testing (temporary) tunable: <description>" ?