Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S267317AbTGaTES (ORCPT ); Thu, 31 Jul 2003 15:04:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267186AbTGaTES (ORCPT ); Thu, 31 Jul 2003 15:04:18 -0400 Received: from e32.co.us.ibm.com ([32.97.110.130]:20668 "EHLO e32.co.us.ibm.com") by vger.kernel.org with ESMTP id S274859AbTGaTEF (ORCPT ); Thu, 31 Jul 2003 15:04:05 -0400 Date: Fri, 1 Aug 2003 00:36:45 +0530 From: Dipankar Sarma To: Andrew Morton Cc: Rusty Russell , Andrea Arcangeli , linux-kernel@vger.kernel.org, "Paul E. McKenney" , cmm@us.ibm.com Subject: Re: [PATCH] RCU: Reduce size of rcu_head 2 of 2 Message-ID: <20030731190645.GD1990@in.ibm.com> Reply-To: dipankar@in.ibm.com References: <20030731185806.GC1990@in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20030731185806.GC1990@in.ibm.com> User-Agent: Mutt/1.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 10497 Lines: 306 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/