Over NFS, an open() call could result in multiple over-the-wire

GETATTRs being generated - one from lookup()/namei() and the other
from nfs_open() (for cto consistency). This change eliminates the
GETATTR in nfs_open() if an otw GETATTR was done from the namei()
path. Instead of extending the vop interface, we timestamp each attr
load, and use this to detect whether a GETATTR was done from namei()
for this syscall. Introduces a thread-local variable that counts the
syscalls made by the thread and uses <pid, tid, thread syscalls> as
the attrload timestamp. Thanks to jhb@ and peter@ for a discussion on
thread state that could be used as the timestamp with minimal overhead.

1 files changed, 1 insertions, 0 deletions

diff --git a/sys/kern/kern_thread.c b/sys/kern/kern_thread.c
index 2fe3bf8..c4a3aa3 100644
--- a/sys/kern/kern_thread.c
+++ b/sys/kern/kern_thread.c
@@ -116,6 +116,7 @@ thread_ctor(void *mem, int size, void *arg, int flags)
 	td->td_oncpu = NOCPU;
 
 	td->td_tid = alloc_unr(tid_unrhdr);
+	td->td_syscalls = 0;
 
 	/*
 	 * Note that td_critnest begins life as 1 because the thread is not