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[34.140.183.197]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48de0bc506asm17915462f8f.47.2026.10.15.01.39.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Oct 2026 01:39:35 -0700 (PDT) Date: Thu, 15 Oct 2026 09:39:31 +0100 From: Vincent Donnefort To: Steven Rostedt Cc: mhiramat@kernel.org, linux-trace-kernel@vger.kernel.org, mathieu.desnoyers@efficios.com, kernel-team@android.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] ring-buffer: Skip si_mem_available() for persistent and remote buffers Message-ID: References: <20261013102047.1488347-1-vdonnefort@google.com> <20261013102047.1488347-2-vdonnefort@google.com> <20261014175126.49c26f93@gandalf.local.home> Precedence: bulk X-Mailing-List: linux-trace-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: <20261014175126.49c26f93@gandalf.local.home> On Wed, Oct 14, 2026 at 05:51:26PM -0400, Steven Rostedt wrote: > On Tue, 13 Oct 2026 11:20:46 +0100 > Vincent Donnefort wrote: > > > Persistent and remote buffer memory is pre-allocated by the time > > __rb_allocate_pages() is called. Skip si_mem_available() to avoid > > wrongly failing the allocation under memory pressure. > > > > For the same reason, unset user_thread. > > > > Fixes: be68d63a139b ("ring-buffer: Add ring_buffer_alloc_range()") > > Fixes: 2e67fabd8b77 ("ring-buffer: Introduce ring-buffer remotes") > > Signed-off-by: Vincent Donnefort > > --- > > kernel/trace/ring_buffer.c | 41 +++++++++++++++++++------------------- > > 1 file changed, 21 insertions(+), 20 deletions(-) > > > > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > > index 04bb94c29f58..b3a30a0413a5 100644 > > --- a/kernel/trace/ring_buffer.c > > +++ b/kernel/trace/ring_buffer.c > > @@ -2442,20 +2442,30 @@ static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, > > struct trace_buffer *buffer = cpu_buffer->buffer; > > struct ring_buffer_cpu_meta *meta = NULL; > > struct buffer_page *bpage, *tmp; > > - bool user_thread = current->mm != NULL; > > struct ring_buffer_desc *desc = NULL; > > + bool user_thread = false; > > long i; > > > > - /* > > - * Check if the available memory is there first. > > - * Note, si_mem_available() only gives us a rough estimate of available > > - * memory. It may not be accurate. But we don't care, we just want > > - * to prevent doing any allocation when it is obvious that it is > > - * not going to succeed. > > - */ > > - i = si_mem_available(); > > - if (i < nr_pages) > > - return -ENOMEM; > > + if (buffer->range_addr_start) { > > + meta = rb_range_meta(buffer, nr_pages, cpu_buffer->cpu); > > + } else if (buffer->remote) { > > + desc = ring_buffer_desc(buffer->remote->desc, cpu_buffer->cpu); > > + if (!desc || WARN_ON(desc->nr_page_va != (nr_pages + 1))) > > + return -EINVAL; > > + } else { > > + /* > > + * Check if the available memory is there first. > > + * Note, si_mem_available() only gives us a rough estimate of available > > + * memory. It may not be accurate. But we don't care, we just want > > + * to prevent doing any allocation when it is obvious that it is > > + * not going to succeed. > > + */ > > + i = si_mem_available(); > > + if (i < nr_pages) > > + return -ENOMEM; > > + > > + user_thread = current->mm != NULL; > > Not caused by this patch but we need to update this to: > > user_thread = is_user_task(current); > > I may add that. I can send a v3 if that helps. -- Vincent > > -- Steve > > > + } > > > > /* > > * If a user thread allocates too much, and si_mem_available() > > @@ -2469,15 +2479,6 @@ static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, > > if (user_thread) > > set_current_oom_origin(); > > > > - if (buffer->range_addr_start) > > - meta = rb_range_meta(buffer, nr_pages, cpu_buffer->cpu); > > - > > - if (buffer->remote) { > > - desc = ring_buffer_desc(buffer->remote->desc, cpu_buffer->cpu); > > - if (!desc || WARN_ON(desc->nr_page_va != (nr_pages + 1))) > > - return -EINVAL; > > - } > > - > > for (i = 0; i < nr_pages; i++) { > > > > bpage = alloc_cpu_page(cpu_buffer->cpu); >