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Message-ID: <20181017111724.GA459@jagdpanzerIV> References: <1539770782-3343-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20181017102821.GM18839@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181017102821.GM18839@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (10/17/18 12:28), Michal Hocko wrote: > > Michal proposed ratelimiting dump_header() [2]. But I don't think that > > that patch is appropriate because that patch does not ratelimit > > > > "%s invoked oom-killer: gfp_mask=%#x(%pGg), nodemask=%*pbl, order=%d, oom_score_adj=%hd\n" > > "Out of memory and no killable processes...\n" [..] > > Let's make sure that next dump_header() waits for at least 60 seconds from > > previous "Out of memory and no killable processes..." message. > > Could you explain why this is any better than using a well established > ratelimit approach? Tetsuo, let's use a well established rate-limit approach both in dump_hedaer() and out_of_memory(). I actually was under impression that Michal added rate-limiting to both of these functions. The appropriate rate-limit value looks like something that printk() should know and be able to tell to the rest of the kernel. I don't think that middle ground will ever be found elsewhere. printk() knows what consoles are registered, and printk() also knows (sometimes) what console="..." options the kernel was provided with. If baud rates ware not provided as console= options, then serial consoles usually use some default value. We can probably ask consoles. So *maybe* we can do something like this // // WARNING: this is just a sketch. A silly idea. // I don't know if we can make it usable. // --- int printk_ratelimit_interval(void) { int ret = DEFAULT_RATELIMIT_INTERVAL; struct tty_driver *driver = NULL; speed_t min_baud = MAX_INT; console_lock(); for_each_console(c) { speed_t br; if (!c->device) continue; if (!(c->flags & CON_ENABLED)) continue; if (!c->write) continue; driver = c->device(c, index); if (!driver) continue; br = tty_get_baud_rate(tty_driver to tty_struct [???]); min_baud = min(min_baud, br); } console_unlock(); switch (min_baud) { case 115200: return ret; case ...blah blah...: return ret * 2; case 9600: return ret * 4; } return ret; } --- -ss