Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756301AbaGaIAu (ORCPT ); Thu, 31 Jul 2014 04:00:50 -0400 Received: from smtp.codeaurora.org ([198.145.11.231]:45375 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756274AbaGaIAt (ORCPT ); Thu, 31 Jul 2014 04:00:49 -0400 From: Chintan Pandya To: akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Chintan Pandya , Thomas Gleixner , John Stultz , Peter Zijlstra , Ingo Molnar , Hugh Dickins Subject: [PATCH v3 2/2] ksm: provide support to use deferrable timers for scanner thread Date: Thu, 31 Jul 2014 13:29:51 +0530 Message-Id: <1406793591-26793-3-git-send-email-cpandya@codeaurora.org> X-Mailer: git-send-email 1.8.2.1 In-Reply-To: <1406793591-26793-2-git-send-email-cpandya@codeaurora.org> References: <1406793591-26793-2-git-send-email-cpandya@codeaurora.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org KSM thread to scan pages is scheduled on definite timeout. That wakes up CPU from idle state and hence may affect the power consumption. Provide an optional support to use deferrable timer which suites low-power use-cases. Typically, on our setup we observed, 10% less power consumption with some use-cases in which CPU goes to power collapse frequently. For example, playing audio while typically CPU remains idle. To enable deferrable timers, $ echo 1 > /sys/kernel/mm/ksm/deferrable_timer Signed-off-by: Chintan Pandya Cc: Thomas Gleixner Cc: John Stultz Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Hugh Dickins --- Changes: V2-->V3: - Handled error case properly - Corrected indentation in Documentation - Fixed build failure - Removed left over process_timeout() V1-->V2: - allowing only valid values to be updated as use_deferrable_timer - using only 'deferrable' and not 'deferred' - moved out schedule_timeout code for deferrable timer into timer.c Documentation/vm/ksm.txt | 7 +++++++ mm/ksm.c | 36 ++++++++++++++++++++++++++++++++++-- 2 files changed, 41 insertions(+), 2 deletions(-) diff --git a/Documentation/vm/ksm.txt b/Documentation/vm/ksm.txt index f34a8ee..9735c87 100644 --- a/Documentation/vm/ksm.txt +++ b/Documentation/vm/ksm.txt @@ -87,6 +87,13 @@ pages_sharing - how many more sites are sharing them i.e. how much saved pages_unshared - how many pages unique but repeatedly checked for merging pages_volatile - how many pages changing too fast to be placed in a tree full_scans - how many times all mergeable areas have been scanned +deferrable_timer - whether to use deferrable timers or not + e.g. "echo 1 > /sys/kernel/mm/ksm/deferrable_timer" + Default: 0 (means, we are not using deferrable timers. Users + might want to set deferrable_timer option if they donot want + ksm thread to wakeup CPU to carryout ksm activities thus + gaining on battery while compromising slightly on memory + that could have been saved.) A high ratio of pages_sharing to pages_shared indicates good sharing, but a high ratio of pages_unshared to pages_sharing indicates wasted effort. diff --git a/mm/ksm.c b/mm/ksm.c index fb75902..434a50a 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -223,6 +223,9 @@ static unsigned int ksm_thread_pages_to_scan = 100; /* Milliseconds ksmd should sleep between batches */ static unsigned int ksm_thread_sleep_millisecs = 20; +/* Boolean to indicate whether to use deferrable timer or not */ +static bool use_deferrable_timer; + #ifdef CONFIG_NUMA /* Zeroed when merging across nodes is not allowed */ static unsigned int ksm_merge_across_nodes = 1; @@ -1725,8 +1728,13 @@ static int ksm_scan_thread(void *nothing) try_to_freeze(); if (ksmd_should_run()) { - schedule_timeout_interruptible( - msecs_to_jiffies(ksm_thread_sleep_millisecs)); + signed long to; + + to = msecs_to_jiffies(ksm_thread_sleep_millisecs); + if (use_deferrable_timer) + schedule_timeout_deferrable_interruptible(to); + else + schedule_timeout_interruptible(to); } else { wait_event_freezable(ksm_thread_wait, ksmd_should_run() || kthread_should_stop()); @@ -2175,6 +2183,29 @@ static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, } KSM_ATTR(run); +static ssize_t deferrable_timer_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return snprintf(buf, 8, "%d\n", use_deferrable_timer); +} + +static ssize_t deferrable_timer_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + unsigned long enable; + int err; + + err = kstrtoul(buf, 10, &enable); + if (err < 0) + return err; + if (enable >= 1) + return -EINVAL; + use_deferrable_timer = enable; + return count; +} +KSM_ATTR(deferrable_timer); + #ifdef CONFIG_NUMA static ssize_t merge_across_nodes_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) @@ -2287,6 +2318,7 @@ static struct attribute *ksm_attrs[] = { &pages_unshared_attr.attr, &pages_volatile_attr.attr, &full_scans_attr.attr, + &deferrable_timer_attr.attr, #ifdef CONFIG_NUMA &merge_across_nodes_attr.attr, #endif -- Chintan Pandya QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/