Messages in this thread Patch in this message | | | Subject | Re: [tip:tracing/ftrace] ftrace: remove struct list_head from struct dyn_ftrace | From | Steven Rostedt <> | Date | Fri, 13 Mar 2009 09:16:30 -0400 |
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On Fri, 2009-03-13 at 10:39 +0000, Lai Jiangshan wrote: > Commit-ID: e94142a67f8bad494c593f0a07c9fc2fbec98c0e > Gitweb: http://git.kernel.org/tip/e94142a67f8bad494c593f0a07c9fc2fbec98c0e > Author: Lai Jiangshan <laijs@cn.fujitsu.com> > AuthorDate: Fri, 13 Mar 2009 17:51:27 +0800 > Commit: Ingo Molnar <mingo@elte.hu> > CommitDate: Fri, 13 Mar 2009 11:36:20 +0100 > > ftrace: remove struct list_head from struct dyn_ftrace > Impact: save memory > > The struct dyn_ftrace table is very large, this patch will save > about 50%. > > Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> > Cc: Steven Rostedt <srostedt@redhat.com> > LKML-Reference: <49BA2C9F.8020009@cn.fujitsu.com> > Signed-off-by: Ingo Molnar <mingo@elte.hu> > > > --- > include/linux/ftrace.h | 1 - > kernel/trace/ftrace.c | 14 ++++++++------ > 2 files changed, 8 insertions(+), 7 deletions(-) > > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h > index c146c10..9d598bb 100644 > --- a/include/linux/ftrace.h > +++ b/include/linux/ftrace.h > @@ -145,7 +145,6 @@ enum { > }; > > struct dyn_ftrace { > - struct list_head list; > unsigned long ip; /* address of mcount call-site */ > unsigned long flags; > struct dyn_arch_ftrace arch; > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index bf78a4c..90d5729 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -272,7 +272,7 @@ enum { > > static int ftrace_filtered; > > -static LIST_HEAD(ftrace_new_addrs); > +static struct dyn_ftrace *ftrace_new_addrs; > > static DEFINE_MUTEX(ftrace_regex_lock); > > @@ -409,8 +409,8 @@ ftrace_record_ip(unsigned long ip) > return NULL; > > rec->ip = ip; > - > - list_add(&rec->list, &ftrace_new_addrs); > + rec->flags = (unsigned long)ftrace_new_addrs;
Lets not play games with pointers. If we are going to do this, make it into a union.
struct dyn_arch_ftrace { unsigned long ip; union { unsigned long flags; struct dyn_arch_ftrace *next; } struct dyn_arch_ftrace arch; };
This way it is much clearer to what is going on.
> + ftrace_new_addrs = rec; > > return rec; > } > @@ -716,19 +716,21 @@ unsigned long ftrace_update_tot_cnt; > > static int ftrace_update_code(struct module *mod) > { > - struct dyn_ftrace *p, *t; > + struct dyn_ftrace *p; > cycle_t start, stop; > > start = ftrace_now(raw_smp_processor_id()); > ftrace_update_cnt = 0; > > - list_for_each_entry_safe(p, t, &ftrace_new_addrs, list) { > + while (ftrace_new_addrs) { > > /* If something went wrong, bail without enabling anything */ > if (unlikely(ftrace_disabled)) > return -1; > > - list_del_init(&p->list); > + p = ftrace_new_addrs; > + ftrace_new_addrs = (struct dyn_ftrace *)p->flags;
This confused me (and scared me) for a bit. Having a union would not have.
Make the change to a union, and then you have my:
Acked-by: Steven Rostedt <srostedt@redhat.com>
Thanks,
-- Steve
> + p->flags = 0L; > > /* convert record (i.e, patch mcount-call with NOP) */ > if (ftrace_code_disable(mod, p)) {
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