From nobody Sun Apr 12 04:22:47 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 53063C19F28 for ; Wed, 3 Aug 2022 10:06:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236251AbiHCKGA (ORCPT ); Wed, 3 Aug 2022 06:06:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48452 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237794AbiHCKFx (ORCPT ); Wed, 3 Aug 2022 06:05:53 -0400 Received: from mail-pl1-x635.google.com (mail-pl1-x635.google.com [IPv6:2607:f8b0:4864:20::635]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7EB13764A for ; Wed, 3 Aug 2022 03:05:51 -0700 (PDT) Received: by mail-pl1-x635.google.com with SMTP id v18so15932755plo.8 for ; Wed, 03 Aug 2022 03:05:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc; bh=bANxufpLCUY+XWPiguyc6Xk+fdLhXPbcV4C2RPgI3FM=; b=CTgvu/TjNHKxvdz52lHLnsHWO3P5bEpln58ylmFson4kOhjVckhXarZUwPPy5FRDxZ Q0gr5DFAUCLSbgjz5aLllSNEp3WL7p5Of1F++OlrXMjVaPLhNqDfuOIez2sWrUilbs+s AymLnmzvsjgTu7EzeEts3SFZZ/VV71kIexvB+QdFaYuqj2BaK7Zk1SADeA2VMcfCQ+TI qN043yUVP5TVIwHSZVdvHmWMysAls8dn6s1GpYsMrX9xd7mbLRIJmD16zWyuoF6esrv1 9nbqR3ntLvsk0ZiT03CqdsDklDBBm7wggbihqhN7qgEmp/M3EXfwkuPRuZ8/3QFpi2hS +lQA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc; bh=bANxufpLCUY+XWPiguyc6Xk+fdLhXPbcV4C2RPgI3FM=; b=Vm1tKPgTWaBdLOEnoLI0+BxQ7RUmy0Y8R1aG9Yv0rp5PNXwNW/VMPfUNDEnH7pMLk6 x0san8lC47iY2gcAfZzPMp54sw6Yg8AklRt57tDEvZrfFXiemnuULI5CI5DYU5ALjmyc B7A4e11Ot8KwKMcPN64gmhCBd70cUO8PIGGYShCDBZo5XUzviQaJiW3F/gkJMbjqsrxV N9/IHK83/9KyV2DBhoxD0+o1aJZsz0bUo64kvE2ffSoRn8H/2vWaRJfzuRnZHC9lqOsw EaekechFIJaW9Mpx6cbnNZliuMnlwCtJ37hVuS+QgDUVnpD2hDbg5ixS2b5LsZI7Cmc3 MobQ== X-Gm-Message-State: ACgBeo2hTBkM5KA7Qqfv2ISZAEkYf3dloqNkmU/BfbHK6Fu0BImhbzU5 0pxD/ay34DZ7xwDXL9sCXVg= X-Google-Smtp-Source: AA6agR6ej/DKKrC02wuJgBsr4b0OO0L2fAyintP2DPnrkyf8wCjR9D+JmfYcQs2tDO6/EciPZsS1Vg== X-Received: by 2002:a17:90b:2c13:b0:1f3:359a:c7d5 with SMTP id rv19-20020a17090b2c1300b001f3359ac7d5mr4162524pjb.72.1659521150810; Wed, 03 Aug 2022 03:05:50 -0700 (PDT) Received: from localhost.localdomain ([193.203.214.57]) by smtp.gmail.com with ESMTPSA id t7-20020a170902e84700b0016e808dbe55sm1499003plg.96.2022.08.03.03.05.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Aug 2022 03:05:50 -0700 (PDT) From: cgel.zte@gmail.com X-Google-Original-From: xu.xin16@zte.con.cn To: akpm@linux-foundation.org Cc: hughd@google.com, izik.eidus@ravellosystems.com, willy@infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, xu xin , CGEL Subject: [RFC PATCH 3/4] ksm: let ksmd work automatically with memory threshold Date: Wed, 3 Aug 2022 10:05:43 +0000 Message-Id: <20220803100543.1653550-1-xu.xin16@zte.con.cn> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220803100306.1653382-1-xu.xin16@zte.con.cn> References: <20220803100306.1653382-1-xu.xin16@zte.con.cn> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: xu xin When memory is sufficient, merging pages to save memory is not very much needed, and it also inceases delays of COW for user application. So set a memory threshold, when free memory is lower than the threshold, ksmd will be triggered to compare and merge pages. And to avoid ping-pong effect due to the threshold, ksmd needs to try to merge pages until free memory is larger than (threshold + total_memory * 1/16). Before free memory is lower than the threshold, ksmd will still scan pages at a very low speed, to calculate their checksum but not to compare and merge pages. | | ----(Threshold + total_memory/16)-------- | | ------Threshold------ | | | |_____ksmd try to merge pages__| We also add a new sysfs klob auto_threshold_percent for user to be able to tune. Signed-off-by: xu xin Signed-off-by: CGEL --- mm/ksm.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 92 insertions(+), 3 deletions(-) diff --git a/mm/ksm.c b/mm/ksm.c index 8acc893e4d61..78819b56efec 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -294,6 +294,17 @@ static unsigned int ksm_max_scanning_factor =3D 32; */ static unsigned int scanning_factor =3D 1; =20 +/* + * Work in auto-mode. + * Default ksm_auto_threshold_percent: 20, means 20%. When free memory + * is lower than total memory * ksm_auto_threshold_percent/100, ksmd will + * be triggered to compare and merge pages. + */ +unsigned int ksm_auto_threshold_percent =3D 20; + +/* Work in auto-mode. Whether trigger ksmd to compare and merge pages */ +static bool auto_triggered; + #ifdef CONFIG_NUMA /* Zeroed when merging across nodes is not allowed */ static unsigned int ksm_merge_across_nodes =3D 1; @@ -2446,11 +2457,46 @@ static void ksm_do_scan(unsigned int scan_npages) rmap_item =3D scan_get_next_rmap_item(&page); if (!rmap_item) return; - cmp_and_merge_page(page, rmap_item); + if (ksm_run & KSM_RUN_AUTO && !auto_triggered) { + /* + * This should happens only when ksm_run is KSM_RUN_AUTO + * and free memory threshold still not reached. + * The reason to calculate it's checksum is to reduce the + * waiting time the rmap_item is added to unstable tree. + */ + rmap_item->oldchecksum =3D calc_checksum(page); + } else + cmp_and_merge_page(page, rmap_item); + put_page(page); } } =20 +/* Work in auto mode, should reset auto_triggered ? */ +static bool should_untrigger_ksmd_to_merge(void) +{ + unsigned long total_ram_pages, free_pages; + + total_ram_pages =3D totalram_pages(); + free_pages =3D global_zone_page_state(NR_FREE_PAGES); + + return free_pages > (total_ram_pages * + ksm_auto_threshold_percent / 100) + + (total_ram_pages >> 4); +} + +/* Work in auto mode, should ksmd start to merge ? */ +static bool should_trigger_ksmd_to_merge(void) +{ + unsigned long total_ram_pages, free_pages; + + total_ram_pages =3D totalram_pages(); + free_pages =3D global_zone_page_state(NR_FREE_PAGES); + + return free_pages < (total_ram_pages * + ksm_auto_threshold_percent / 100); +} + static int ksmd_should_run(void) { if (!list_empty(&ksm_mm_head.mm_list)) @@ -2469,8 +2515,18 @@ static int ksm_scan_thread(void *nothing) mutex_lock(&ksm_thread_mutex); wait_while_offlining(); if (ksmd_should_run()) { - if (ksm_run & KSM_RUN_AUTO) - ksm_do_scan(ksm_thread_pages_to_scan * scanning_factor); + if (ksm_run & KSM_RUN_AUTO) { + /* + * If free memory is not lower than threshold, we only scan + * 5 pages and just calculate pages' checksum and not compare + * and merge them. Otherwise, do real scanning and merging as + * scanning-enhanced algorithm. + */ + if (!auto_triggered) + ksm_do_scan(5); + else + ksm_do_scan(ksm_thread_pages_to_scan * scanning_factor); + } else ksm_do_scan(ksm_thread_pages_to_scan); } @@ -2491,6 +2547,11 @@ static int ksm_scan_thread(void *nothing) reset_scanning_factor(); =20 ksm_scan.new_ksmpages_of_this_scanning =3D 0; + + if (should_trigger_ksmd_to_merge()) + auto_triggered =3D true; + else if (should_untrigger_ksmd_to_merge()) + auto_triggered =3D false; } =20 try_to_freeze(); @@ -3035,6 +3096,32 @@ static ssize_t max_scanning_factor_store(struct kobj= ect *kobj, } KSM_ATTR(max_scanning_factor); =20 +static ssize_t auto_threshold_percent_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sysfs_emit(buf, "%u\n", ksm_auto_threshold_percent); +} + +static ssize_t auto_threshold_percent_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + unsigned int value; + int err; + + err =3D kstrtouint(buf, 10, &value); + if (err) + return -EINVAL; + + if (value > 100) + return -EINVAL; + + ksm_auto_threshold_percent =3D value; + + return count; +} +KSM_ATTR(auto_threshold_percent); + #ifdef CONFIG_NUMA static ssize_t merge_across_nodes_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) @@ -3246,6 +3333,7 @@ static struct attribute *ksm_attrs[] =3D { &pages_to_scan_attr.attr, &run_attr.attr, &max_scanning_factor_attr.attr, + &auto_threshold_percent_attr.attr, &pages_shared_attr.attr, &pages_sharing_attr.attr, &pages_unshared_attr.attr, @@ -3277,6 +3365,7 @@ static int __init ksm_init(void) zero_checksum =3D calc_checksum(ZERO_PAGE(0)); /* Default to false for backwards compatibility */ ksm_use_zero_pages =3D false; + auto_triggered =3D false; =20 err =3D ksm_slab_init(); if (err) --=20 2.25.1