lkml.org 
[lkml]   [2003]   [Jul]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH] RCU: Reduce size of rcu_head 2 of 2
This is the second part of Rusty's idea - using container_of to
get to the RCU protected structure given the rcu_head in the
callback. It assumes that the rcu_head is embedded in that structure.
This along with the singly-linked rcu_head patch reduces the
size of struct rcu_head by 50%. With rcu_head being used in dentries
and dst_entries, this is useful savings. It does require changes
in call_rcu() API. I have tested the 2 patches with some sanity
tests (dcache/route cache) and RCU works fine.

Thanks
Dipankar



This is a merge of Rusty's patch to save space in rcu_heads
along with the changes required to all the call_rcu() users.
It changes the call_rcu() API and avoids passing an
argument to the callback function. Instead, it is assumed that
the user has embedded the rcu head into a structure that is
useful in the callback and the rcu_head pointer is passed to
the callback. The callback can use container_of() to get the
pointer to its structure and work with it. Together with
the rcu-singly-link patch, it reduces the rcu_head size
by 50%. Considering that we use these in things like
struct dentry and struct dst_entry, this is good savings
in space.


fs/dcache.c | 6 +++---
include/linux/rcupdate.h | 10 ++++------
include/net/dst.h | 6 ++++++
ipc/util.c | 25 ++++++++++++++++++++-----
kernel/rcupdate.c | 25 +++++++++++++++----------
net/bridge/br_if.c | 7 ++++---
net/decnet/dn_route.c | 4 ++--
net/ipv4/route.c | 4 ++--
8 files changed, 56 insertions(+), 31 deletions(-)

diff -puN include/linux/rcupdate.h~rcu-no-arg include/linux/rcupdate.h
--- linux-2.6.0-test2-rcu/include/linux/rcupdate.h~rcu-no-arg 2003-07-31 16:13:19.000000000 +0530
+++ linux-2.6.0-test2-rcu-dipankar/include/linux/rcupdate.h 2003-07-31 16:13:19.000000000 +0530
@@ -44,18 +44,16 @@
* struct rcu_head - callback structure for use with RCU
* @next: next update requests in a list
* @func: actual update function to call after the grace period.
- * @arg: argument to be passed to the actual update function.
*/
struct rcu_head {
struct rcu_head *next;
- void (*func)(void *obj);
- void *arg;
+ void (*func)(struct rcu_head *head);
};

-#define RCU_HEAD_INIT(head) { .next = NULL, .func = NULL, .arg = NULL }
+#define RCU_HEAD_INIT(head) { .next = NULL, .func = NULL }
#define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT(head)
#define INIT_RCU_HEAD(ptr) do { \
- (ptr)->next = NULL; (ptr)->func = NULL; (ptr)->arg = NULL; \
+ (ptr)->next = NULL; (ptr)->func = NULL; \
} while (0)


@@ -127,7 +125,7 @@ extern void rcu_check_callbacks(int cpu,

/* Exported interfaces */
extern void FASTCALL(call_rcu(struct rcu_head *head,
- void (*func)(void *arg), void *arg));
+ void (*func)(struct rcu_head *head)));
extern void synchronize_kernel(void);

#endif /* __KERNEL__ */
diff -puN kernel/rcupdate.c~rcu-no-arg kernel/rcupdate.c
--- linux-2.6.0-test2-rcu/kernel/rcupdate.c~rcu-no-arg 2003-07-31 16:13:19.000000000 +0530
+++ linux-2.6.0-test2-rcu-dipankar/kernel/rcupdate.c 2003-07-31 16:13:19.000000000 +0530
@@ -59,20 +59,18 @@ static DEFINE_PER_CPU(struct tasklet_str
* call_rcu - Queue an RCU update request.
* @head: structure to be used for queueing the RCU updates.
* @func: actual update function to be invoked after the grace period
- * @arg: argument to be passed to the update function
*
* The update function will be invoked as soon as all CPUs have performed
* a context switch or been seen in the idle loop or in a user process.
* The read-side of critical section that use call_rcu() for updation must
* be protected by rcu_read_lock()/rcu_read_unlock().
*/
-void call_rcu(struct rcu_head *head, void (*func)(void *arg), void *arg)
+void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
{
int cpu;
unsigned long flags;

head->func = func;
- head->arg = arg;
head->next = NULL;
local_irq_save(flags);
cpu = smp_processor_id();
@@ -91,7 +89,7 @@ static void rcu_do_batch(struct rcu_head

while (list) {
next = list->next;
- list->func(list->arg);
+ list->func(list);
list = next;
}
}
@@ -239,11 +237,18 @@ void __init rcu_init(void)
register_cpu_notifier(&rcu_nb);
}

+struct rcu_synchronize {
+ struct rcu_head head;
+ struct completion completion;
+};

/* Because of FASTCALL declaration of complete, we use this wrapper */
-static void wakeme_after_rcu(void *completion)
+static void wakeme_after_rcu(struct rcu_head *head)
{
- complete(completion);
+ struct rcu_synchronize *rcu;
+
+ rcu = container_of(head, struct rcu_synchronize, head);
+ complete(&rcu->completion);
}

/**
@@ -252,14 +257,14 @@ static void wakeme_after_rcu(void *compl
*/
void synchronize_kernel(void)
{
- struct rcu_head rcu;
- DECLARE_COMPLETION(completion);
+ struct rcu_synchronize rcu;

+ init_completion(&rcu.completion);
/* Will wake me after RCU finished */
- call_rcu(&rcu, wakeme_after_rcu, &completion);
+ call_rcu(&rcu.head, wakeme_after_rcu);

/* Wait for it */
- wait_for_completion(&completion);
+ wait_for_completion(&rcu.completion);
}


diff -puN fs/dcache.c~rcu-no-arg fs/dcache.c
--- linux-2.6.0-test2-rcu/fs/dcache.c~rcu-no-arg 2003-07-31 16:13:19.000000000 +0530
+++ linux-2.6.0-test2-rcu-dipankar/fs/dcache.c 2003-07-31 16:13:19.000000000 +0530
@@ -58,9 +58,9 @@ struct dentry_stat_t dentry_stat = {
.age_limit = 45,
};

-static void d_callback(void *arg)
+static void d_callback(struct rcu_head *head)
{
- struct dentry * dentry = (struct dentry *)arg;
+ struct dentry * dentry = container_of(head, struct dentry, d_rcu);

if (dname_external(dentry)) {
kfree(dentry->d_qstr);
@@ -76,7 +76,7 @@ static void d_free(struct dentry *dentry
{
if (dentry->d_op && dentry->d_op->d_release)
dentry->d_op->d_release(dentry);
- call_rcu(&dentry->d_rcu, d_callback, dentry);
+ call_rcu(&dentry->d_rcu, d_callback);
}

/*
diff -puN ipc/util.c~rcu-no-arg ipc/util.c
--- linux-2.6.0-test2-rcu/ipc/util.c~rcu-no-arg 2003-07-31 16:13:19.000000000 +0530
+++ linux-2.6.0-test2-rcu-dipankar/ipc/util.c 2003-07-31 16:13:19.000000000 +0530
@@ -332,25 +332,40 @@ void* ipc_rcu_alloc(int size)
* Since RCU callback function is called in bh,
* we need to defer the vfree to schedule_work
*/
-static void ipc_schedule_free(void* arg)
+static void ipc_schedule_free(struct rcu_head *head)
{
- struct ipc_rcu_vmalloc *free = arg;
+ struct ipc_rcu_vmalloc *free =
+ container_of(head, struct ipc_rcu_vmalloc, rcu);

INIT_WORK(&free->work, vfree, free);
schedule_work(&free->work);
}

+/**
+ * ipc_immediate_free - free ipc + rcu space
+ *
+ * Free from the RCU callback context
+ *
+ */
+static void ipc_immediate_free(struct rcu_head *head)
+{
+ struct ipc_rcu_kmalloc *free =
+ container_of(head, struct ipc_rcu_kmalloc, rcu);
+ kfree(free);
+}
+
+
+
void ipc_rcu_free(void* ptr, int size)
{
if (rcu_use_vmalloc(size)) {
struct ipc_rcu_vmalloc *free;
free = ptr - sizeof(*free);
- call_rcu(&free->rcu, ipc_schedule_free, free);
+ call_rcu(&free->rcu, ipc_schedule_free);
} else {
struct ipc_rcu_kmalloc *free;
free = ptr - sizeof(*free);
- /* kfree takes a "const void *" so gcc warns. So we cast. */
- call_rcu(&free->rcu, (void (*)(void *))kfree, free);
+ call_rcu(&free->rcu, ipc_immediate_free);
}

}
diff -puN net/bridge/br_if.c~rcu-no-arg net/bridge/br_if.c
--- linux-2.6.0-test2-rcu/net/bridge/br_if.c~rcu-no-arg 2003-07-31 16:13:19.000000000 +0530
+++ linux-2.6.0-test2-rcu-dipankar/net/bridge/br_if.c 2003-07-31 16:16:33.000000000 +0530
@@ -38,9 +38,10 @@ static int br_initial_port_cost(struct n
return 100;
}

-static void destroy_nbp(void *arg)
+static void destroy_nbp(struct rcu_head *head)
{
- struct net_bridge_port *p = arg;
+ struct net_bridge_port *p =
+ container_of(head, struct net_bridge_port, rcu);

p->dev->br_port = NULL;

@@ -69,7 +70,7 @@ static void del_nbp(struct net_bridge_po
del_timer(&p->forward_delay_timer);
del_timer(&p->hold_timer);

- call_rcu(&p->rcu, destroy_nbp, p);
+ call_rcu(&p->rcu, destroy_nbp);
}

static void del_br(struct net_bridge *br)
diff -puN net/decnet/dn_route.c~rcu-no-arg net/decnet/dn_route.c
--- linux-2.6.0-test2-rcu/net/decnet/dn_route.c~rcu-no-arg 2003-07-31 16:13:19.000000000 +0530
+++ linux-2.6.0-test2-rcu-dipankar/net/decnet/dn_route.c 2003-07-31 16:13:19.000000000 +0530
@@ -145,14 +145,14 @@ static __inline__ unsigned dn_hash(unsig

static inline void dnrt_free(struct dn_route *rt)
{
- call_rcu(&rt->u.dst.rcu_head, (void (*)(void *))dst_free, &rt->u.dst);
+ call_rcu(&rt->u.dst.rcu_head, dst_rcu_free);
}

static inline void dnrt_drop(struct dn_route *rt)
{
if (rt)
dst_release(&rt->u.dst);
- call_rcu(&rt->u.dst.rcu_head, (void (*)(void *))dst_free, &rt->u.dst);
+ call_rcu(&rt->u.dst.rcu_head, dst_rcu_free);
}

static void dn_dst_check_expire(unsigned long dummy)
diff -puN include/net/dst.h~rcu-no-arg include/net/dst.h
--- linux-2.6.0-test2-rcu/include/net/dst.h~rcu-no-arg 2003-07-31 16:13:19.000000000 +0530
+++ linux-2.6.0-test2-rcu-dipankar/include/net/dst.h 2003-07-31 16:13:19.000000000 +0530
@@ -182,6 +182,12 @@ static inline void dst_free(struct dst_e
__dst_free(dst);
}

+static inline void dst_rcu_free(struct rcu_head *head)
+{
+ struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head);
+ dst_free(dst);
+}
+
static inline void dst_confirm(struct dst_entry *dst)
{
if (dst)
diff -puN net/ipv4/route.c~rcu-no-arg net/ipv4/route.c
--- linux-2.6.0-test2-rcu/net/ipv4/route.c~rcu-no-arg 2003-07-31 16:13:19.000000000 +0530
+++ linux-2.6.0-test2-rcu-dipankar/net/ipv4/route.c 2003-07-31 16:13:19.000000000 +0530
@@ -411,13 +411,13 @@ void __init rt_cache_proc_exit(void)

static __inline__ void rt_free(struct rtable *rt)
{
- call_rcu(&rt->u.dst.rcu_head, (void (*)(void *))dst_free, &rt->u.dst);
+ call_rcu(&rt->u.dst.rcu_head, dst_rcu_free);
}

static __inline__ void rt_drop(struct rtable *rt)
{
ip_rt_put(rt);
- call_rcu(&rt->u.dst.rcu_head, (void (*)(void *))dst_free, &rt->u.dst);
+ call_rcu(&rt->u.dst.rcu_head, dst_rcu_free);
}

static __inline__ int rt_fast_clean(struct rtable *rth)
_
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:47    [W:0.066 / U:0.712 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site