Re: [PATCH v3 31/35] lib: add memory allocations report in show_mem()

Michal Hocko
2024-02-15T16:45:06Z

On Thu 15-02-24 06:58:42, Suren Baghdasaryan wrote:
> On Thu, Feb 15, 2024 at 1:22 AM Michal Hocko <mhocko@suse.com> wrote:
> >
> > On Mon 12-02-24 13:39:17, Suren Baghdasaryan wrote:
> > [...]
> > > @@ -423,4 +424,18 @@ void __show_mem(unsigned int filter, nodemask_t *nodemask, int max_zone_idx)
> > > #ifdef CONFIG_MEMORY_FAILURE
> > > printk("%lu pages hwpoisoned\n", atomic_long_read(&num_poisoned_pages));
> > > #endif
> > > +#ifdef CONFIG_MEM_ALLOC_PROFILING
> > > + {
> > > + struct seq_buf s;
> > > + char *buf = kmalloc(4096, GFP_ATOMIC);
> > > +
> > > + if (buf) {
> > > + printk("Memory allocations:\n");
> > > + seq_buf_init(&s, buf, 4096);
> > > + alloc_tags_show_mem_report(&s);
> > > + printk("%s", buf);
> > > + kfree(buf);
> > > + }
> > > + }
> > > +#endif
> >
> > I am pretty sure I have already objected to this. Memory allocations in
> > the oom path are simply no go unless there is absolutely no other way
> > around that. In this case the buffer could be preallocated.
>
> Good point. We will change this to a smaller buffer allocated on the
> stack and will print records one-by-one. Thanks!

__show_mem could be called with a very deep call chains. A single
pre-allocated buffer should just do ok.

--
Michal Hocko
SUSE Labs