On Sun, 16 Oct 2005, Dipankar Sarma wrote:
>
> Linus, I don't think this has anything to do with RCU grace periods
> like we discussed previously. I measured on my 3.6GHz x86_64 and
> found that open()/close() pair on /dev/null takes about 45500
> cycles or 12 microseconds. [Does that sound resonable?].
That sounds very slow. I can do a million open/close pairs in 4 seconds on
a 2.5GHz G5. Maybe you tested a cold-cache case?
Of course, a P4 is just about the worst architecture to test system call
performance on, so ...
Still, that's 4us. I'm pretty sure some machines will do it in 3 or less
(in fact, lmbench says 3.17us on another machine of mine for open/close).
Still, that's only four times faster, so 2 timer ticks should be less than
5000 file structs to free.
I suspect this patch is worth it for the 2.6.14 timeframe, but I'll wait
for confirmation.
In fact, for 2.6.14, I'd almost do an even more minimal one. I agree with
your changing the file counter to an atomic, but I'd rather keep that
change for later.
Serge, does this alternate patch work for you?
[ cache constructors and destructors are _stupid_. They act exactly the
wrong way from a cache standpoint. ]
Linus
---
diff --git a/fs/dcache.c b/fs/dcache.c
index fb10386..40aaa90 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1731,7 +1731,7 @@ void __init vfs_caches_init(unsigned lon
SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
- SLAB_HWCACHE_ALIGN|SLAB_PANIC, filp_ctor, filp_dtor);
+ SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
dcache_init(mempages);
inode_init(mempages);
diff --git a/fs/file_table.c b/fs/file_table.c
index 86ec8ae..fbda480 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -39,21 +39,9 @@ void filp_ctor(void * objp, struct kmem_
{
if ((cflags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
SLAB_CTOR_CONSTRUCTOR) {
- unsigned long flags;
- spin_lock_irqsave(&filp_count_lock, flags);
- files_stat.nr_files++;
- spin_unlock_irqrestore(&filp_count_lock, flags);
}
}
-void filp_dtor(void * objp, struct kmem_cache_s *cachep, unsigned long dflags)
-{
- unsigned long flags;
- spin_lock_irqsave(&filp_count_lock, flags);
- files_stat.nr_files--;
- spin_unlock_irqrestore(&filp_count_lock, flags);
-}
-
static inline void file_free_rcu(struct rcu_head *head)
{
struct file *f = container_of(head, struct file, f_rcuhead);
@@ -62,6 +50,13 @@ static inline void file_free_rcu(struct
static inline void file_free(struct file *f)
{
+ unsigned long flags;
+
+ /* Stupid. Use atomics */
+ spin_lock_irqsave(&filp_count_lock, flags);
+ files_stat.nr_files--;
+ spin_unlock_irqrestore(&filp_count_lock, flags);
+
call_rcu(&f->f_rcuhead, file_free_rcu);
}
@@ -73,6 +68,7 @@ struct file *get_empty_filp(void)
{
static int old_max;
struct file * f;
+ unsigned long flags;
/*
* Privileged users can go above max_files
@@ -85,6 +81,11 @@ struct file *get_empty_filp(void)
if (f == NULL)
goto fail;
+ /* Stupid. Use atomics */
+ spin_lock_irqsave(&filp_count_lock, flags);
+ files_stat.nr_files++;
+ spin_unlock_irqrestore(&filp_count_lock, flags);
+
memset(f, 0, sizeof(*f));
if (security_file_alloc(f))
goto fail_sec;
diff --git a/include/linux/file.h b/include/linux/file.h
index f5bbd4c..55f0572 100644
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -60,8 +60,6 @@ extern void put_filp(struct file *);
extern int get_unused_fd(void);
extern void FASTCALL(put_unused_fd(unsigned int fd));
struct kmem_cache_s;
-extern void filp_ctor(void * objp, struct kmem_cache_s *cachep, unsigned long cflags);
-extern void filp_dtor(void * objp, struct kmem_cache_s *cachep, unsigned long dflags);
extern struct file ** alloc_fd_array(int);
extern void free_fd_array(struct file **, int);
-
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