Messages in this thread | | | Date | Mon, 20 Oct 2008 11:43:19 -0400 | From | Mathieu Desnoyers <> | Subject | Re: [PATCH tip/tracing/markers] markers: simplify marker_set_format() |
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* Lai Jiangshan (laijs@cn.fujitsu.com) wrote: > Mathieu Desnoyers wrote: > > * Lai Jiangshan (laijs@cn.fujitsu.com) wrote: > >> current marker_set_format() is complex this patch simplify it, > >> and decrease the overhead of marker_update_probes(). > >> > > > > Yep, I think I did put the format string after the name \0, which was > > rather tricky. I agree that such change makes the code more readable at > > the expense of doing 2 allocations per marker rather than one, but > > readability might be a good thing here. > > this fix did help for readability and made code cleanly. > but it's still 1 allocation per marker_entry when format != NULL. > the previous benefit is not lost. >
Yes, but the common case is to have format != NULL, so it's 2 alloc per marker. :)
Mathieu
> Thanks, Lai > > > > > Thanks ! > > > > Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> > > > >> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> > >> --- > >> diff --git a/kernel/marker.c b/kernel/marker.c > >> index e49a9c5..ef43c86 100644 > >> --- a/kernel/marker.c > >> +++ b/kernel/marker.c > >> @@ -65,6 +65,7 @@ struct marker_entry { > >> void *oldptr; > >> int rcu_pending; > >> unsigned char ptype:1; > >> + unsigned char format_allocated:1; > >> char name[0]; /* Contains name'\0'format'\0' */ > >> }; > >> > >> @@ -415,6 +416,7 @@ static struct marker_entry *add_marker(const char *name, const char *format) > >> e->single.probe_private = NULL; > >> e->multi = NULL; > >> e->ptype = 0; > >> + e->format_allocated = 0; > >> e->refcount = 0; > >> e->rcu_pending = 0; > >> hlist_add_head(&e->hlist, head); > >> @@ -446,6 +448,8 @@ static int remove_marker(const char *name) > >> if (e->single.func != __mark_empty_function) > >> return -EBUSY; > >> hlist_del(&e->hlist); > >> + if (e->format_allocated) > >> + kfree(e->format); > >> /* Make sure the call_rcu has been executed */ > >> if (e->rcu_pending) > >> rcu_barrier_sched(); > >> @@ -456,57 +460,34 @@ static int remove_marker(const char *name) > >> /* > >> * Set the mark_entry format to the format found in the element. > >> */ > >> -static int marker_set_format(struct marker_entry **entry, const char *format) > >> +static int marker_set_format(struct marker_entry *entry, const char *format) > >> { > >> - struct marker_entry *e; > >> - size_t name_len = strlen((*entry)->name) + 1; > >> - size_t format_len = strlen(format) + 1; > >> - > >> - > >> - e = kmalloc(sizeof(struct marker_entry) + name_len + format_len, > >> - GFP_KERNEL); > >> - if (!e) > >> + entry->format = kstrdup(format, GFP_KERNEL); > >> + if (!entry->format) > >> return -ENOMEM; > >> - memcpy(&e->name[0], (*entry)->name, name_len); > >> - e->format = &e->name[name_len]; > >> - memcpy(e->format, format, format_len); > >> - if (strcmp(e->format, MARK_NOARGS) == 0) > >> - e->call = marker_probe_cb_noarg; > >> - else > >> - e->call = marker_probe_cb; > >> - e->single = (*entry)->single; > >> - e->multi = (*entry)->multi; > >> - e->ptype = (*entry)->ptype; > >> - e->refcount = (*entry)->refcount; > >> - e->rcu_pending = 0; > >> - hlist_add_before(&e->hlist, &(*entry)->hlist); > >> - hlist_del(&(*entry)->hlist); > >> - /* Make sure the call_rcu has been executed */ > >> - if ((*entry)->rcu_pending) > >> - rcu_barrier_sched(); > >> - kfree(*entry); > >> - *entry = e; > >> + entry->format_allocated = 1; > >> + > >> trace_mark(core_marker_format, "name %s format %s", > >> - e->name, e->format); > >> + entry->name, entry->format); > >> return 0; > >> } > >> > >> /* > >> * Sets the probe callback corresponding to one marker. > >> */ > >> -static int set_marker(struct marker_entry **entry, struct marker *elem, > >> +static int set_marker(struct marker_entry *entry, struct marker *elem, > >> int active) > >> { > >> int ret; > >> - WARN_ON(strcmp((*entry)->name, elem->name) != 0); > >> + WARN_ON(strcmp(entry->name, elem->name) != 0); > >> > >> - if ((*entry)->format) { > >> - if (strcmp((*entry)->format, elem->format) != 0) { > >> + if (entry->format) { > >> + if (strcmp(entry->format, elem->format) != 0) { > >> printk(KERN_NOTICE > >> "Format mismatch for probe %s " > >> "(%s), marker (%s)\n", > >> - (*entry)->name, > >> - (*entry)->format, > >> + entry->name, > >> + entry->format, > >> elem->format); > >> return -EPERM; > >> } > >> @@ -522,34 +503,33 @@ static int set_marker(struct marker_entry **entry, struct marker *elem, > >> * pass from a "safe" callback (with argument) to an "unsafe" > >> * callback (does not set arguments). > >> */ > >> - elem->call = (*entry)->call; > >> + elem->call = entry->call; > >> /* > >> * Sanity check : > >> * We only update the single probe private data when the ptr is > >> * set to a _non_ single probe! (0 -> 1 and N -> 1, N != 1) > >> */ > >> WARN_ON(elem->single.func != __mark_empty_function > >> - && elem->single.probe_private > >> - != (*entry)->single.probe_private && > >> - !elem->ptype); > >> - elem->single.probe_private = (*entry)->single.probe_private; > >> + && elem->single.probe_private != entry->single.probe_private > >> + && !elem->ptype); > >> + elem->single.probe_private = entry->single.probe_private; > >> /* > >> * Make sure the private data is valid when we update the > >> * single probe ptr. > >> */ > >> smp_wmb(); > >> - elem->single.func = (*entry)->single.func; > >> + elem->single.func = entry->single.func; > >> /* > >> * We also make sure that the new probe callbacks array is consistent > >> * before setting a pointer to it. > >> */ > >> - rcu_assign_pointer(elem->multi, (*entry)->multi); > >> + rcu_assign_pointer(elem->multi, entry->multi); > >> /* > >> * Update the function or multi probe array pointer before setting the > >> * ptype. > >> */ > >> smp_wmb(); > >> - elem->ptype = (*entry)->ptype; > >> + elem->ptype = entry->ptype; > >> elem->state = active; > >> > >> return 0; > >> @@ -593,8 +573,7 @@ void marker_update_probe_range(struct marker *begin, > >> for (iter = begin; iter < end; iter++) { > >> mark_entry = get_marker(iter->name); > >> if (mark_entry) { > >> - set_marker(&mark_entry, iter, > >> - !!mark_entry->refcount); > >> + set_marker(mark_entry, iter, !!mark_entry->refcount); > >> /* > >> * ignore error, continue > >> */ > >> @@ -656,7 +635,7 @@ int marker_probe_register(const char *name, const char *format, > >> ret = PTR_ERR(entry); > >> } else if (format) { > >> if (!entry->format) > >> - ret = marker_set_format(&entry, format); > >> + ret = marker_set_format(entry, format); > >> else if (strcmp(entry->format, format)) > >> ret = -EPERM; > >> } > >> > >> > >> > >> > >> > > > >
-- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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