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Tue, 13 Feb 2024 15:32:21 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap2.dmz-prg2.suse.org with ESMTPSA id NYe6FYWLy2UPfQAAn2gu4w (envelope-from ); Tue, 13 Feb 2024 15:32:21 +0000 Date: Tue, 13 Feb 2024 16:33:30 +0100 From: Oscar Salvador To: Vlastimil Babka Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Marco Elver , Andrey Konovalov , Alexander Potapenko Subject: Re: [PATCH v8 3/5] mm,page_owner: Display all stacks and their count Message-ID: References: <20240212223029.30769-1-osalvador@suse.de> <20240212223029.30769-4-osalvador@suse.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Authentication-Results: smtp-out2.suse.de; none X-Spamd-Result: default: False [-7.00 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_GOOD(-0.10)[text/plain]; REPLY(-4.00)[]; RCVD_COUNT_THREE(0.00)[3]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; RCPT_COUNT_SEVEN(0.00)[8]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; FREEMAIL_CC(0.00)[linux-foundation.org,vger.kernel.org,kvack.org,suse.com,google.com,gmail.com]; RCVD_TLS_ALL(0.00)[]; BAYES_HAM(-2.90)[99.57%] X-Spam-Level: X-Spam-Flag: NO X-Spam-Score: -7.00 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