Messages in this thread | | | Date | Tue, 14 Oct 2008 11:53:22 +0800 | From | Lai Jiangshan <> | Subject | Re: [PATCH] v3 rudimentary tracing for Classic RCU |
| |
Paul E. McKenney wrote: > Hello! > > This is v3 of a tracing patch for Classic RCU, which creates "rcu/rcucb" > and "rcu/rcudata" files in debugfs. This patch can be handy when you > need to work out why RCU is refusing to end the current grace period. > > Should be ready for inclusion in tip/core/rcu, Ingo, please apply.
Hi, Paul,
I'm sorry that I'm a little busy these days, so I have not ported it to seq_file, and you lost one choice.
I found that seq_cpumask_list() is needed when I tried to ported v2 to seq_file, so I introduced seq_cpumask_list() for seq_file, I'm waiting procfs hackers apply that patch too.
Lai.
> > Changes since v2: Add flag to rcu_data to avoid printing rcu_data for > CPUs that have never been online. > > Add documentation (below). > > Changes since v1: Adds (crude) tracing for rcu_data structures. > > Reading from the "rcu/rcucb" file results in something like the following: > > rcu: cur=1129 completed=1128 pending=0 s=0 > 0,3,7
use "somename: 0,3,7" ? then when mask is empty, I think "somename:" is better than empty line.
> rcu_bh: cur=-287 completed=-287 pending=0 s=0 > > online: 0-7 > > The first two lines are for rcu, the second two for rcu_bh. The cur= > is the current grace-period number, and the completed= is the number > of the last completed grace period. If these two numbers are equal, > the corresponding flavor of RCU is idle. The pending= is the furthest > future batch number that is required, if equal to cur=, no additional > grace periods are required. The s=, if non-zero, indicates that a round > of reschedule IPIs has been send to attempt to expedite the current > grace period. > > The second and fourth lines are a comma/dash-separated list of > the CPUs that have not yet reported a quiescent state for the > current grace period (CPUs 0, 3, and 7 for "rcu" above). > > The last line lists the online CPUs. > > > Reading from the "rcu/rcudata" file results in the following: > > rcu: > 0 qb=885 b=884 pq=1 qsp=0 ql=0 bl=10 > 1 qb=885 b=882 pq=1 qsp=0 ql=2 bl=10 > 2 qb=885 b=854 pq=1 qsp=0 ql=0 bl=10 > 3 qb=885 b=885 pq=1 qsp=0 ql=0 bl=10 > rcu_bh: > 0 qb=-291 b=-291 pq=1 qsp=0 ql=0 bl=10 > 1 qb=-291 b=0 pq=1 qsp=0 ql=0 bl=10 > 2 qb=-291 b=0 pq=1 qsp=0 ql=0 bl=10 > 3 qb=-291 b=-298 pq=1 qsp=0 ql=0 bl=10 > > This output is again split into rcu and rcu_bh portions. Within each > portion, there is one line per CPU, but only for those CPUs that have > been online at least once since boot. The number at the beginning of > each line is the CPU number, followed by an "!" if the corresponding CPU > is currently offline. The qb= is the batch number for the RCU core, > the b= is the batch number corresponding to the callbacks waiting for > the current grace period for this CPU, the pq= is a flag indicating that > this CPU has passed through a quiescent state for the current grace > period, the qsp= is a flag indicating that the RCU core has been > informed that this CPU has passed through a quiescent state for the > current grace period, the ql= is the number of RCU callbacks currently > enqueued on this CPU (regardless of their state), and the bl= is the > current limit of the number of callbacks to be invoked at one shot. > > Tested on x86 and Power, rebased to -tip. > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > --- > > include/linux/rcuclassic.h | 4 + > kernel/Kconfig.preempt | 1 > kernel/Makefile | 2 > kernel/rcuclassic.c | 5 - > kernel/rcuclassic_trace.c | 179 +++++++++++++++++++++++++++++++++++++++++++++ > 5 files changed, 188 insertions(+), 3 deletions(-) > > diff --git a/include/linux/rcuclassic.h b/include/linux/rcuclassic.h > index 5f89b62..ce183a8 100644 > --- a/include/linux/rcuclassic.h > +++ b/include/linux/rcuclassic.h > @@ -63,6 +63,9 @@ struct rcu_ctrlblk { > /* for current batch to proceed. */ > } ____cacheline_internodealigned_in_smp; > > +extern struct rcu_ctrlblk rcu_ctrlblk; > +extern struct rcu_ctrlblk rcu_bh_ctrlblk; > + > /* Is batch a before batch b ? */ > static inline int rcu_batch_before(long a, long b) > { > @@ -81,6 +84,7 @@ struct rcu_data { > long quiescbatch; /* Batch # for grace period */ > int passed_quiesc; /* User-mode/idle loop etc. */ > int qs_pending; /* core waits for quiesc state */ > + bool beenonline; /* CPU online at least once */ > > /* 2) batch handling */ > /* > diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt > index 9fdba03..ba32338 100644 > --- a/kernel/Kconfig.preempt > +++ b/kernel/Kconfig.preempt > @@ -68,7 +68,6 @@ config PREEMPT_RCU > > config RCU_TRACE > bool "Enable tracing for RCU - currently stats in debugfs" > - depends on PREEMPT_RCU > select DEBUG_FS > default y > help > diff --git a/kernel/Makefile b/kernel/Makefile > index 4e1d7df..e0bfce7 100644 > --- a/kernel/Makefile > +++ b/kernel/Makefile > @@ -77,6 +77,8 @@ obj-$(CONFIG_CLASSIC_RCU) += rcuclassic.o > obj-$(CONFIG_PREEMPT_RCU) += rcupreempt.o > ifeq ($(CONFIG_PREEMPT_RCU),y) > obj-$(CONFIG_RCU_TRACE) += rcupreempt_trace.o > +else > +obj-$(CONFIG_RCU_TRACE) += rcuclassic_trace.o > endif > obj-$(CONFIG_RELAY) += relay.o > obj-$(CONFIG_SYSCTL) += utsname_sysctl.o > diff --git a/kernel/rcuclassic.c b/kernel/rcuclassic.c > index 37f72e5..54bd23b 100644 > --- a/kernel/rcuclassic.c > +++ b/kernel/rcuclassic.c > @@ -58,14 +58,14 @@ EXPORT_SYMBOL_GPL(rcu_lock_map); > > > /* Definition for rcupdate control block. */ > -static struct rcu_ctrlblk rcu_ctrlblk = { > +struct rcu_ctrlblk rcu_ctrlblk = { > .cur = -300, > .completed = -300, > .pending = -300, > .lock = __SPIN_LOCK_UNLOCKED(&rcu_ctrlblk.lock), > .cpumask = CPU_MASK_NONE, > }; > -static struct rcu_ctrlblk rcu_bh_ctrlblk = { > +struct rcu_ctrlblk rcu_bh_ctrlblk = { > .cur = -300, > .completed = -300, > .pending = -300, > @@ -725,6 +725,7 @@ static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp, > rdp->donetail = &rdp->donelist; > rdp->quiescbatch = rcp->completed; > rdp->qs_pending = 0; > + rdp->beenonline = 1; > rdp->cpu = cpu; > rdp->blimit = blimit; > spin_unlock_irqrestore(&rcp->lock, flags); > diff --git a/kernel/rcuclassic_trace.c b/kernel/rcuclassic_trace.c > new file mode 100644 > index 0000000..d19780b > --- /dev/null > +++ b/kernel/rcuclassic_trace.c > @@ -0,0 +1,179 @@ > +/* > + * Read-Copy Update tracing for classic implementation > + * > + * This program is free software; you can redistribute it and/or modify > + * it under the terms of the GNU General Public License as published by > + * the Free Software Foundation; either version 2 of the License, or > + * (at your option) any later version. > + * > + * This program is distributed in the hope that it will be useful, > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + * GNU General Public License for more details. > + * > + * You should have received a copy of the GNU General Public License > + * along with this program; if not, write to the Free Software > + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. > + * > + * Copyright IBM Corporation, 2008 > + * > + * Papers: http://www.rdrop.com/users/paulmck/RCU > + * > + * For detailed explanation of Read-Copy Update mechanism see - > + * Documentation/RCU > + * > + */ > +#include <linux/types.h> > +#include <linux/kernel.h> > +#include <linux/init.h> > +#include <linux/spinlock.h> > +#include <linux/smp.h> > +#include <linux/rcupdate.h> > +#include <linux/interrupt.h> > +#include <linux/sched.h> > +#include <asm/atomic.h> > +#include <linux/bitops.h> > +#include <linux/module.h> > +#include <linux/completion.h> > +#include <linux/moduleparam.h> > +#include <linux/percpu.h> > +#include <linux/notifier.h> > +#include <linux/cpu.h> > +#include <linux/mutex.h> > +#include <linux/debugfs.h> > + > +static DEFINE_MUTEX(rcuclassic_trace_mutex); > +static char *rcuclassic_trace_buf; > +#define RCUCLASSIC_TRACE_BUF_SIZE (128 * num_possible_cpus() + 100) > + > +static int print_one_rcu_data(struct rcu_data *rdp, char *buf, char *ebuf) > +{ > + int cnt = 0; > + > + if (!rdp->beenonline) > + return 0; > + cnt += snprintf(&buf[cnt], ebuf - &buf[cnt], > + "%3d%cqb=%ld b=%ld pq=%d qsp=%d ql=%ld bl=%ld\n", > + rdp->cpu, cpu_is_offline(rdp->cpu) ? '!' : ' ', > + rdp->quiescbatch, rdp->batch, rdp->passed_quiesc, > + rdp->qs_pending, rdp->qlen, rdp->blimit); > + return cnt; > +} > + > +#define PRINT_RCU_DATA(name, buf, ebuf) \ > + do { \ > + int _p_r_d_i; \ > + \ > + for_each_possible_cpu(_p_r_d_i) \ > + (buf) += print_one_rcu_data(&per_cpu(name, _p_r_d_i), \ > + buf, ebuf); \ > + } while (0) > + > +static ssize_t rcudata_read(struct file *filp, char __user *buffer, > + size_t count, loff_t *ppos) > +{ > + ssize_t bcount; > + char *buf = rcuclassic_trace_buf; > + char *ebuf = &rcuclassic_trace_buf[RCUCLASSIC_TRACE_BUF_SIZE]; > + > + mutex_lock(&rcuclassic_trace_mutex); > + buf += snprintf(buf, ebuf - buf, "rcu:\n"); > + PRINT_RCU_DATA(rcu_data, buf, ebuf); > + buf += snprintf(buf, ebuf - buf, "rcu_bh:\n"); > + PRINT_RCU_DATA(rcu_bh_data, buf, ebuf); > + bcount = simple_read_from_buffer(buffer, count, ppos, > + rcuclassic_trace_buf, strlen(rcuclassic_trace_buf));
Is strlen(rcuclassic_trace_buf) == buf - rcuclassic_trace_buf ?
> + mutex_unlock(&rcuclassic_trace_mutex); > + return bcount; > +} > + > +static int print_one_rcu_ctrlblk(struct rcu_ctrlblk *rcp, char *buf, char *ebuf) > +{ > + int cnt = 0; > + > + cnt += snprintf(&buf[cnt], ebuf - &buf[cnt], "cur=%ld completed=%ld " > + "pending=%ld s=%d\n\t", > + rcp->cur, rcp->completed, > + rcp->pending, rcp->signaled); > + cnt += cpulist_scnprintf(&buf[cnt], ebuf - &buf[cnt], rcp->cpumask); > + cnt += snprintf(&buf[cnt], ebuf - &buf[cnt], "\n"); > + return cnt; > +} > + > +static ssize_t rcucb_read(struct file *filp, char __user *buffer, > + size_t count, loff_t *ppos) > +{ > + ssize_t bcount; > + char *buf = rcuclassic_trace_buf; > + char *ebuf = &rcuclassic_trace_buf[RCUCLASSIC_TRACE_BUF_SIZE]; > + > + mutex_lock(&rcuclassic_trace_mutex); > + buf += snprintf(buf, ebuf - buf, "rcu: "); > + buf += print_one_rcu_ctrlblk(&rcu_ctrlblk, buf, ebuf); > + buf += snprintf(buf, ebuf - buf, "rcu_bh: "); > + buf += print_one_rcu_ctrlblk(&rcu_bh_ctrlblk, buf, ebuf); > + buf += snprintf(buf, ebuf - buf, "online: "); > + buf += cpulist_scnprintf(buf, ebuf - buf, cpu_online_map); > + buf += snprintf(buf, ebuf - buf, "\n"); > + bcount = simple_read_from_buffer(buffer, count, ppos, > + rcuclassic_trace_buf, strlen(rcuclassic_trace_buf)); > + mutex_unlock(&rcuclassic_trace_mutex); > + return bcount; > +} > + > +static struct file_operations rcudata_fops = { > + .owner = THIS_MODULE, > + .read = rcudata_read, > +}; > + > +static struct file_operations rcucb_fops = { > + .owner = THIS_MODULE, > + .read = rcucb_read, > +}; > + > +static struct dentry *rcudir, *datadir, *cbdir; > +static int rcuclassic_debugfs_init(void) > +{ > + rcudir = debugfs_create_dir("rcu", NULL); > + if (!rcudir) > + goto out; > + datadir = debugfs_create_file("rcudata", 0444, rcudir, > + NULL, &rcudata_fops); > + if (!datadir) > + goto free_out; > + cbdir = debugfs_create_file("rcucb", 0444, rcudir, NULL, &rcucb_fops); > + if (!cbdir) > + goto free_out; > + return 0; > +free_out: > + if (datadir) > + debugfs_remove(datadir); > + debugfs_remove(rcudir); > +out: > + return 1; > +} > + > +static int __init rcuclassic_trace_init(void) > +{ > + int ret; > + > + rcuclassic_trace_buf = kmalloc(RCUCLASSIC_TRACE_BUF_SIZE, GFP_KERNEL); > + if (!rcuclassic_trace_buf) > + return 1; > + ret = rcuclassic_debugfs_init(); > + if (ret) > + kfree(rcuclassic_trace_buf); > + return ret; > +} > + > +static void __exit rcuclassic_trace_cleanup(void) > +{ > + debugfs_remove(datadir); > + debugfs_remove(cbdir); > + debugfs_remove(rcudir); > + kfree(rcuclassic_trace_buf); > +} > + > + > +module_init(rcuclassic_trace_init); > +module_exit(rcuclassic_trace_cleanup);
should have: MODULE_LICENSE("GPL");
optional but recommend: MODULE_AUTHOR("Paul E. McKenney"); MODULE_DESCRIPTION("DESCRIPTION");
> -- > 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/ > > >
| |