On Tue, Feb 13, 2024 at 03:25:26PM +0100, Vlastimil Babka wrote:
> On 2/12/24 23:30, Oscar Salvador wrote:
> > +static int stack_print(struct seq_file *m, void *v)
> > +{
> > + char *buf;
> > + int ret = 0;
> > + struct stack *stack = v;
> > + struct stack_record *stack_record = stack->stack_record;
> > +
> > + if (!stack_record->size || stack_record->size < 0 ||
> > + refcount_read(&stack_record->count) < 2)
> > + return 0;
> > +
> > + buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
> > +
> > + ret += stack_trace_snprint(buf, PAGE_SIZE, stack_record->entries,
> > + stack_record->size, 0);
> > + if (!ret)
> > + goto out;
> > +
> > + scnprintf(buf + ret, PAGE_SIZE - ret, "stack_count: %d\n\n",
> > + refcount_read(&stack_record->count));
> > +
> > + seq_printf(m, buf);
> > + seq_puts(m, "\n\n");
> > +out:
> > + kfree(buf);
>
> Seems rather wasteful to do kzalloc/kfree so you can print into that buffer
> first and then print/copy it again using seq_printf. If you give up on using
> stack_trace_snprintf() it's not much harder to print the stack directly with
> a loop of seq_printf. See e.g. slab_debugfs_show().
Well, I thought about not reinventing the wheel there, but fair enough
than performing a kmalloc/free op on every print might be suboptimal.
I will try to do ir with seq_printf alone.
Thanks
--
Oscar Salvador
SUSE Labs
