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Tue, 13 Feb 2024 15:36:01 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id M+mrMWGMy2VzQAAAD6G6ig (envelope-from ); Tue, 13 Feb 2024 15:36:01 +0000 Message-ID: Date: Tue, 13 Feb 2024 16:36:01 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 3/5] mm,page_owner: Display all stacks and their count Content-Language: en-US To: Oscar Salvador Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Marco Elver , Andrey Konovalov , Alexander Potapenko References: <20240212223029.30769-1-osalvador@suse.de> <20240212223029.30769-4-osalvador@suse.de> From: Vlastimil Babka In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 569D780020 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: mne9hu39iemnyphm1euqmd6pa7bctowm X-HE-Tag: 1707838563-242945 X-HE-Meta: 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 2ZGMWkP+ pYJjJmInXTr75f/uF6fASVr+lNiKI9NsKJi/gB6jBWz12+KJmXXarV1QKOxlkyywCTHWbGfmewg5F8zMxA/LTsPLkE67V6kG9X8xv6GS5TDJ6RwCmpYkZZTQraA5NbB0PLKUTI5isp4+eh9E25mRGtEBNKuE5Y9HyDNw/RU+1HFCrFK8cb0yOnvcl94RPrmDJJDZaRXkCPcCiDOM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/13/24 16:33, Oscar Salvador wrote: > 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. Of course once there's more than one stackdepot user printing into a seq_file, creating a common seq_file helper analogy of stack_trace_snprintf() and using it from all places, would also be an option :) > Thanks > >