Contents:
1) takes unhash_process() into sched.c, moves zeroing ->pid into it (and
under tasklist_lock
2) new helper in fs/proc/base.c - name_to_int(dentry) returns ~0U if name
doesn't match 0|[1-9][0-9]* or is too large. Otherwise it returns
numeric value of name. proc_pid_lookup() and proc_lookupfd() converted.
3) sane dentry retention. Namely, we don't kill /proc/<pid> dentries at the
first opportunity (as the current tree does). Instead we do the following:
* ->d_delete() kills it only if process is already dead.
* all ->lookup() in proc/base.c end with checking if process is still
alive and unhash if it isn't.
* proc_pid_lookup() (lookup for /proc/<pid>) caches reference to dentry
in task_struct. It's _not_ counted in ->d_count.
* ->d_iput() resets said reference to NULL.
* release_task() (burying a zombie) checks if there is a cached
reference and if there is - shrinks the subtree.
* tasklist_lock is used for exclusion.
That way we are guaranteed that after release_task() all dentries in
/proc/<pid> will go away as soon as possible; OTOH, before release_task()
we have normal retention policy - they go away under memory pressure with
the same rules as for dentries on any other fs.
4) preparation to sane policy for /proc/<pid>/fd/* - we don't store
struct file * in these inodes anymore.
5) sane retention policy for /proc/<pid>/fd/* - ->d_revalidate() says
"kill it" if descriptor is not opened anymore (in addition to checks
for task being dead) and we allow dentries of /proc/<pid>/fd/<n> to
stay around.
Patchset eliminates a _lot_ of allocation/freeing/guaranteed negative dcache
lookups for procfs. It seems to be working here, but I would really appreciate
help with testing/review.
First chunk follows, the rest will go in separate mails.
diff -urN C8-0/include/linux/sched.h C8-unhash_process/include/linux/sched.h
--- C8-0/include/linux/sched.h Sun Apr 14 17:53:12 2002
+++ C8-unhash_process/include/linux/sched.h Fri Apr 19 01:16:35 2002
@@ -769,15 +769,7 @@
#define thread_group_leader(p) (p->pid == p->tgid)
-static inline void unhash_process(struct task_struct *p)
-{
- write_lock_irq(&tasklist_lock);
- nr_threads--;
- unhash_pid(p);
- REMOVE_LINKS(p);
- list_del(&p->thread_group);
- write_unlock_irq(&tasklist_lock);
-}
+extern void unhash_process(struct task_struct *p);
/* Protects ->fs, ->files, ->mm, and synchronises with wait4(). Nests inside tasklist_lock */
static inline void task_lock(struct task_struct *p)
diff -urN C8-0/kernel/exit.c C8-unhash_process/kernel/exit.c
--- C8-0/kernel/exit.c Sun Apr 14 17:53:13 2002
+++ C8-unhash_process/kernel/exit.c Fri Apr 19 01:16:35 2002
@@ -27,6 +27,17 @@
int getrusage(struct task_struct *, int, struct rusage *);
+static inline void __unhash_process(struct task_struct *p)
+{
+ write_lock_irq(&tasklist_lock);
+ nr_threads--;
+ unhash_pid(p);
+ REMOVE_LINKS(p);
+ list_del(&p->thread_group);
+ p->pid = 0;
+ write_unlock_irq(&tasklist_lock);
+}
+
static void release_task(struct task_struct * p)
{
if (p == current)
@@ -43,8 +54,14 @@
current->cmaj_flt += p->maj_flt + p->cmaj_flt;
current->cnswap += p->nswap + p->cnswap;
sched_exit(p);
- p->pid = 0;
put_task_struct(p);
+}
+
+/* we are using it only for SMP init */
+
+void unhash_process(struct task_struct *p)
+{
+ return __unhash_process(p);
}
/*
-
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This archive was generated by hypermail 2b29 : Tue Apr 23 2002 - 22:00:26 EST