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.p...@gmail.com> wrote:
On Saturday, January 23, 2021, Mateusz Guzik <m...@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 <m...@freebsd.org>
AuthorDate: 2021-01-23 17:21:42 +0000
Commit:     Mateusz Guzik <m...@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
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Could we:

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