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[209.85.220.65]) by mx.google.com with SMTPS id u81sor4856104oie.88.2019.03.12.10.45.26 for (Google Transport Security); Tue, 12 Mar 2019 10:45:26 -0700 (PDT) Received-SPF: pass (google.com: domain of sultan.kerneltoast@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; spf=pass (google.com: domain of sultan.kerneltoast@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=sultan.kerneltoast@gmail.com X-Google-Smtp-Source: APXvYqye0hnmv7pAGXdBIolazCUN2OVPVRFmxBCKF9wVuEGFBFrjN4yDlavLRNISW9yrF7O+Mdtchg== X-Received: by 2002:aca:6cc9:: with SMTP id h192mr2487951oic.161.1552412726061; Tue, 12 Mar 2019 10:45:26 -0700 (PDT) Received: from sultan-box.localdomain ([107.193.118.89]) by smtp.gmail.com with ESMTPSA id x3sm3536175otg.52.2019.03.12.10.45.24 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 12 Mar 2019 10:45:25 -0700 (PDT) Date: Tue, 12 Mar 2019 10:45:20 -0700 From: Sultan Alsawaf To: Tim Murray Cc: Michal Hocko , Suren Baghdasaryan , Greg Kroah-Hartman , Arve =?iso-8859-1?B?SGr4bm5lduVn?= , Todd Kjos , Martijn Coenen , Joel Fernandes , Christian Brauner , Ingo Molnar , Peter Zijlstra , LKML , devel@driverdev.osuosl.org, linux-mm Subject: Re: [RFC] simple_lmk: Introduce Simple Low Memory Killer for Android Message-ID: <20190312174520.GA9276@sultan-box.localdomain> References: <20190310203403.27915-1-sultan@kerneltoast.com> <20190311174320.GC5721@dhcp22.suse.cz> <20190311175800.GA5522@sultan-box.localdomain> <20190311204626.GA3119@sultan-box.localdomain> <20190312080532.GE5721@dhcp22.suse.cz> <20190312163741.GA2762@sultan-box.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.3 (2019-02-01) 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: On Tue, Mar 12, 2019 at 10:17:43AM -0700, Tim Murray wrote: > Knowing whether a SIGKILL'd process has finished reclaiming is as far > as I know not possible without something like procfds. That's where > the 100ms timeout in lmkd comes in. lowmemorykiller and lmkd both > attempt to wait up to 100ms for reclaim to finish by checking for the > continued existence of the thread that received the SIGKILL, but this > really means that they wait up to 100ms for the _thread_ to finish, > which doesn't tell you anything about the memory used by that process. > If those threads terminate early and lowmemorykiller/lmkd get a signal > to kill again, then there may be two processes competing for CPU time > to reclaim memory. That doesn't reclaim any faster and may be an > unnecessary kill. > ... > - offer a way to wait for process termination so lmkd can tell when > reclaim has finished and know when killing another process is > appropriate Should be pretty easy with something like this: diff --git a/include/linux/sched.h b/include/linux/sched.h index 1549584a1..6ac478af2 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1199,6 +1199,7 @@ struct task_struct { unsigned long lowest_stack; unsigned long prev_lowest_stack; #endif + ktime_t sigkill_time; /* * New fields for task_struct should be added above here, so that diff --git a/kernel/fork.c b/kernel/fork.c index 9dcd18aa2..0ae182777 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -435,6 +435,8 @@ void put_task_stack(struct task_struct *tsk) void free_task(struct task_struct *tsk) { + ktime_t sigkill_time = tsk->sigkill_time; + pid_t pid = tsk->pid; #ifndef CONFIG_THREAD_INFO_IN_TASK /* * The task is finally done with both the stack and thread_info, @@ -455,6 +457,9 @@ void free_task(struct task_struct *tsk) if (tsk->flags & PF_KTHREAD) free_kthread_struct(tsk); free_task_struct(tsk); + if (sigkill_time) + printk("%d killed after %lld us\n", pid, + ktime_us_delta(ktime_get(), sigkill_time)); } EXPORT_SYMBOL(free_task); @@ -1881,6 +1886,7 @@ static __latent_entropy struct task_struct *copy_process( p->sequential_io = 0; p->sequential_io_avg = 0; #endif + p->sigkill_time = 0; /* Perform scheduler related setup. Assign this task to a CPU. */ retval = sched_fork(clone_flags, p); diff --git a/kernel/signal.c b/kernel/signal.c index 5d53183e2..1142c8811 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1168,6 +1168,8 @@ static int __send_signal(int sig, struct kernel_siginfo *info, struct task_struc } out_set: + if (sig == SIGKILL) + t->sigkill_time = ktime_get(); signalfd_notify(t, sig); sigaddset(&pending->signal, sig);