From patchwork Mon Dec 4 23:49:03 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Roesch X-Patchwork-Id: 173601 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:bcd1:0:b0:403:3b70:6f57 with SMTP id r17csp3110048vqy; Mon, 4 Dec 2023 15:49:47 -0800 (PST) X-Google-Smtp-Source: AGHT+IHeQ7p2kkPS4VPrecTFlMe+JQRM3balE6mB/xkNcS3YO6BbRDrKaYRiGfRvB4+LlQePnho8 X-Received: by 2002:a05:6830:10c2:b0:6d8:79f0:6d04 with SMTP id z2-20020a05683010c200b006d879f06d04mr4116332oto.4.1701733786802; Mon, 04 Dec 2023 15:49:46 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1701733786; cv=none; d=google.com; s=arc-20160816; b=dhEyNZh5PNGYTCc6MJIOl02aR5EQrqlCuLP2HFgicOTcpXb59r68cYMH10X2+sXzb2 cLNM1mlafB0sDTRa4V4QfJDEGSjvF/H+HbNbN1CrIa7dSa/jyCGqL5OToiE54WV7Y49X jaGwAtTkVL68OjPFShUiO2Kw5bYxtyj6IiwbOY824GUdis4b5I3h/8xkLEpK02ngN+Mh UYvq2adPxEs9Vog/OgO6N+OVSYDuWRiqJVnpcXUJyz/kL8Qns3avE/WEo0GGzvIJX4Km 7BacpVzvva9glD9g6ZVYcdutwX2xq/BRIvkpk5Uj3Bd+KbcUmKTywC4jdZMW7YjYMVxS /OwQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from; bh=/VTrMN/BrcioFf/k17fIgK+kv8rzuRZxzS2IvYcj0/E=; fh=sS+J4OyOC0EcVLWJpS3mBHGeO+0+dYZJ+ImCUfzsrH4=; b=i9AHcrCiq3w/nemftOw5fAc7mco3rOGyJGcMHl/Y8eTnxwDLXjGoo8GSEOvnOgzD0i RmaQLBZBWzylKMrhz0F8QdKB3rwAwTw0L5NiJHTlhLimgyJ0yJ7UeHzAHwYKmp9+aQsC 4kuzeT3h9DdZJDiUmKg9RG/C+j7wkw2eetLHv6EkHyd36K+hELpnaV3hAhrusoP1WD5Z qBm86Eo7xlkG6J/t9kHdsewFsRGnz3G29JjcCyn1rtsdK5eKgOosYvhZ9UZV1QF57ipT GvGiVPAjJuNbg6m+VlGZg5eL60Zl+LiLMUIFU5JL8UKOUOVdQtPvuIilqf0v6EiY+Q/5 97GA== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:7 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from snail.vger.email (snail.vger.email. [2620:137:e000::3:7]) by mx.google.com with ESMTPS id z20-20020a656654000000b005c6921c1cddsi2127971pgv.143.2023.12.04.15.49.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 Dec 2023 15:49:46 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:7 as permitted sender) client-ip=2620:137:e000::3:7; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:7 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by snail.vger.email (Postfix) with ESMTP id B157780B01F1; Mon, 4 Dec 2023 15:49:45 -0800 (PST) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.11 at snail.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343594AbjLDXt2 (ORCPT + 99 others); Mon, 4 Dec 2023 18:49:28 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45330 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343493AbjLDXtQ (ORCPT ); Mon, 4 Dec 2023 18:49:16 -0500 Received: from 66-220-144-178.mail-mxout.facebook.com (66-220-144-178.mail-mxout.facebook.com [66.220.144.178]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C0CD1107 for ; Mon, 4 Dec 2023 15:49:21 -0800 (PST) Received: by devbig1114.prn1.facebook.com (Postfix, from userid 425415) id 41A8F105D3A7B; Mon, 4 Dec 2023 15:49:08 -0800 (PST) From: Stefan Roesch To: kernel-team@fb.com Cc: shr@devkernel.io, akpm@linux-foundation.org, david@redhat.com, hannes@cmpxchg.org, riel@surriel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v3 1/4] mm/ksm: add ksm advisor Date: Mon, 4 Dec 2023 15:49:03 -0800 Message-Id: <20231204234906.1237478-2-shr@devkernel.io> X-Mailer: git-send-email 2.39.3 In-Reply-To: <20231204234906.1237478-1-shr@devkernel.io> References: <20231204234906.1237478-1-shr@devkernel.io> MIME-Version: 1.0 X-Spam-Status: No, score=0.1 required=5.0 tests=BAYES_00,HELO_MISC_IP, RCVD_IN_DNSWL_BLOCKED,RDNS_DYNAMIC,SPF_HELO_PASS,SPF_NEUTRAL, TVD_RCVD_IP,T_SCC_BODY_TEXT_LINE autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (snail.vger.email [0.0.0.0]); Mon, 04 Dec 2023 15:49:45 -0800 (PST) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1784397207087572684 X-GMAIL-MSGID: 1784397207087572684 This adds the ksm advisor. The ksm advisor automatically manages the pages_to_scan setting to achieve a target scan time. The target scan time defines how many seconds it should take to scan all the candidate KSM pages. In other words the pages_to_scan rate is changed by the advisor to achieve the target scan time. The algorithm has a max and min value to: - guarantee responsiveness to changes - limit CPU resource consumption The respective parameters are: - ksm_advisor_target_scan_time (how many seconds a scan should take) - ksm_advisor_max_cpu (maximum value for cpu percent usage) - ksm_advisor_min_pages (minimum value for pages_to_scan per batch) - ksm_advisor_max_pages (maximum value for pages_to_scan per batch) The algorithm calculates the change value based on the target scan time and the previous scan time. To avoid pertubations an exponentially weighted moving average is applied. The advisor is managed by two main parameters: target scan time, cpu max time for the ksmd background thread. These parameters determine how aggresive ksmd scans. In addition there are min and max values for the pages_to_scan parameter to make sure that its initial and max values are not set too low or too high. This ensures that it is able to react to changes quickly enough. The default values are: - target scan time: 200 secs - max cpu: 70% - min pages: 500 - max pages: 30000 By default the advisor is disabled. Currently there are two advisors: none and scan-time. Tests with various workloads have shown considerable CPU savings. Most of the workloads I have investigated have more candidate pages during startup, once the workload is stable in terms of memory, the number of candidate pages is reduced. Without the advisor, the pages_to_scan needs to be sized for the maximum number of candidate pages. So having this advisor definitely helps in reducing CPU consumption. For the instagram workload, the advisor achieves a 25% CPU reduction. Once the memory is stable, the pages_to_scan parameter gets reduced to about 40% of its max value. Signed-off-by: Stefan Roesch Acked-by: David Hildenbrand --- mm/ksm.c | 175 ++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 174 insertions(+), 1 deletion(-) diff --git a/mm/ksm.c b/mm/ksm.c index 7efcc68ccc6ea..b27010fa2e946 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -21,6 +21,7 @@ #include #include #include +#include #include #include #include @@ -248,6 +249,9 @@ static struct kmem_cache *rmap_item_cache; static struct kmem_cache *stable_node_cache; static struct kmem_cache *mm_slot_cache; +/* Default number of pages to scan per batch */ +#define DEFAULT_PAGES_TO_SCAN 100 + /* The number of pages scanned */ static unsigned long ksm_pages_scanned; @@ -276,7 +280,7 @@ static unsigned int ksm_stable_node_chains_prune_millisecs = 2000; static int ksm_max_page_sharing = 256; /* Number of pages ksmd should scan in one batch */ -static unsigned int ksm_thread_pages_to_scan = 100; +static unsigned int ksm_thread_pages_to_scan = DEFAULT_PAGES_TO_SCAN; /* Milliseconds ksmd should sleep between batches */ static unsigned int ksm_thread_sleep_millisecs = 20; @@ -297,6 +301,168 @@ unsigned long ksm_zero_pages; /* The number of pages that have been skipped due to "smart scanning" */ static unsigned long ksm_pages_skipped; +/* Don't scan more than max pages per batch. */ +static unsigned long ksm_advisor_max_pages = 30000; + +/* At least scan this many pages per batch. */ +static unsigned long ksm_advisor_min_pages = 500; + +/* Min CPU for scanning pages per scan */ +static unsigned int ksm_advisor_min_cpu = 10; + +/* Max CPU for scanning pages per scan */ +static unsigned int ksm_advisor_max_cpu = 70; + +/* Target scan time in seconds to analyze all KSM candidate pages. */ +static unsigned long ksm_advisor_target_scan_time = 200; + +/* Exponentially weighted moving average. */ +#define EWMA_WEIGHT 30 + +/** + * struct advisor_ctx - metadata for KSM advisor + * @start_scan: start time of the current scan + * @scan_time: scan time of previous scan + * @change: change in percent to pages_to_scan parameter + * @cpu_time: cpu time consumed by the ksmd thread in the previous scan + */ +struct advisor_ctx { + ktime_t start_scan; + unsigned long scan_time; + unsigned long change; + unsigned long long cpu_time; +}; +static struct advisor_ctx advisor_ctx; + +/* Define different advisor's */ +enum ksm_advisor_type { + KSM_ADVISOR_NONE, + KSM_ADVISOR_SCAN_TIME, +}; +static enum ksm_advisor_type ksm_advisor; + +static void init_advisor(void) +{ + advisor_ctx = (const struct advisor_ctx){ 0 }; +} + +static void set_advisor_defaults(void) +{ + if (ksm_advisor == KSM_ADVISOR_NONE) + ksm_thread_pages_to_scan = DEFAULT_PAGES_TO_SCAN; + else if (ksm_advisor == KSM_ADVISOR_SCAN_TIME) + ksm_thread_pages_to_scan = ksm_advisor_min_pages; +} + +static inline void advisor_start_scan(void) +{ + if (ksm_advisor == KSM_ADVISOR_SCAN_TIME) + advisor_ctx.start_scan = ktime_get(); +} + +static inline s64 advisor_stop_scan(void) +{ + return ktime_ms_delta(ktime_get(), advisor_ctx.start_scan); +} + +/* + * Use previous scan time if available, otherwise use current scan time as an + * approximation for the previous scan time. + */ +static inline unsigned long prev_scan_time(struct advisor_ctx *ctx, + unsigned long scan_time) +{ + return ctx->scan_time ? ctx->scan_time : scan_time; +} + +/* Calculate exponential weighted moving average */ +static unsigned long ewma(unsigned long prev, unsigned long curr) +{ + return ((100 - EWMA_WEIGHT) * prev + EWMA_WEIGHT * curr) / 100; +} + +/* + * The scan time advisor is based on the current scan rate and the target + * scan rate. + * + * new_pages_to_scan = pages_to_scan * (scan_time / target_scan_time) + * + * To avoid pertubations it calculates a change factor of previous changes. + * A new change factor is calculated for each iteration and it uses an + * exponentially weighted moving average. The new pages_to_scan value is + * multiplied with that change factor: + * + * new_pages_to_scan *= change facor + * + * In addition the new pages_to_scan value is capped by the max and min + * limits. + */ +static void scan_time_advisor(void) +{ + unsigned int cpu_percent; + unsigned long cpu_time; + unsigned long cpu_time_diff; + unsigned long cpu_time_diff_ms; + unsigned long pages; + unsigned long per_page_cost; + unsigned long factor; + unsigned long change; + unsigned long last_scan_time; + s64 scan_time; + + /* Convert scan time to seconds */ + scan_time = advisor_stop_scan(); + scan_time = div_s64(scan_time, MSEC_PER_SEC); + scan_time = scan_time ? scan_time : 1; + + /* Calculate CPU consumption of ksmd background thread */ + cpu_time = task_sched_runtime(current); + cpu_time_diff = cpu_time - advisor_ctx.cpu_time; + cpu_time_diff_ms = cpu_time_diff / 1000 / 1000; + + cpu_percent = (cpu_time_diff_ms * 100) / (scan_time * 1000); + cpu_percent = cpu_percent ? cpu_percent : 1; + last_scan_time = prev_scan_time(&advisor_ctx, scan_time); + + /* Calculate scan time as percentage of target scan time */ + factor = ksm_advisor_target_scan_time * 100 / scan_time; + factor = factor ? factor : 1; + + /* + * Calculate scan time as percentage of last scan time and use + * exponentially weighted average to smooth it + */ + change = scan_time * 100 / last_scan_time; + change = change ? change : 1; + change = ewma(advisor_ctx.change, change); + + /* Calculate new scan rate based on target scan rate. */ + pages = ksm_thread_pages_to_scan * 100 / factor; + /* Update pages_to_scan by weighted change percentage. */ + pages = pages * change / 100; + + /* Cap new pages_to_scan value */ + per_page_cost = ksm_thread_pages_to_scan / cpu_percent; + per_page_cost = per_page_cost ? per_page_cost : 1; + + pages = min(pages, per_page_cost * ksm_advisor_max_cpu); + pages = max(pages, per_page_cost * ksm_advisor_min_cpu); + pages = min(pages, ksm_advisor_max_pages); + + /* Update advisor context */ + advisor_ctx.change = change; + advisor_ctx.scan_time = scan_time; + advisor_ctx.cpu_time = cpu_time; + + ksm_thread_pages_to_scan = pages; +} + +static void run_advisor(void) +{ + if (ksm_advisor == KSM_ADVISOR_SCAN_TIME) + scan_time_advisor(); +} + #ifdef CONFIG_NUMA /* Zeroed when merging across nodes is not allowed */ static unsigned int ksm_merge_across_nodes = 1; @@ -2401,6 +2567,7 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) mm_slot = ksm_scan.mm_slot; if (mm_slot == &ksm_mm_head) { + advisor_start_scan(); trace_ksm_start_scan(ksm_scan.seqnr, ksm_rmap_items); /* @@ -2558,6 +2725,8 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) if (mm_slot != &ksm_mm_head) goto next_mm; + run_advisor(); + trace_ksm_stop_scan(ksm_scan.seqnr, ksm_rmap_items); ksm_scan.seqnr++; return NULL; @@ -3244,6 +3413,9 @@ static ssize_t pages_to_scan_store(struct kobject *kobj, unsigned int nr_pages; int err; + if (ksm_advisor != KSM_ADVISOR_NONE) + return -EINVAL; + err = kstrtouint(buf, 10, &nr_pages); if (err) return -EINVAL; @@ -3603,6 +3775,7 @@ static int __init ksm_init(void) zero_checksum = calc_checksum(ZERO_PAGE(0)); /* Default to false for backwards compatibility */ ksm_use_zero_pages = false; + init_advisor(); err = ksm_slab_init(); if (err) From patchwork Mon Dec 4 23:49:04 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Roesch X-Patchwork-Id: 173600 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:bcd1:0:b0:403:3b70:6f57 with SMTP id r17csp3110029vqy; Mon, 4 Dec 2023 15:49:44 -0800 (PST) X-Google-Smtp-Source: AGHT+IGXsCl1n+XtuOaG9XeKNlYFm+JpSffa7yBuO9UaTgGFJ8CHmUdwonaskaLyE+wOnROScvxg X-Received: by 2002:a05:6a20:9f9b:b0:18f:97c:9792 with SMTP id mm27-20020a056a209f9b00b0018f097c9792mr7572396pzb.122.1701733783943; Mon, 04 Dec 2023 15:49:43 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1701733783; cv=none; d=google.com; s=arc-20160816; b=Rid1e+UXpGfOj1aairyCGF//jGvg0Cp7Oic+eNOOU0FyahBrfUB9nCCuN4C8a1cHlb 8/kSdiRT02mHpVyTZbjLXt2Zx6fL3I66CBVucQXd05uZdhc59EMcO4Z/IEe7WFhmXNWA K6y1/0MRcMs4sjd4XaUiWn/gkzYSx7DkK6WiGz8DuGlkot1iSkq7XZXoc90n2iDa9XXs 6fo6/NHhu2C2jI0bjB0QVhc7RomdoZ3RwHKmpQW03/zWCMihzi6Mwd8Af4pY95SZfLGE 4aRL7m5dBm3UtkCiwt6aopExy0biUznV50rBVhbkOQoeClckdBbT9x0CmIe0v0IWf+y+ Q8ig== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from; bh=lSOH/I2hSe0+XvfrQBNIjBmF6L0o2lUHd9hlQ8s2gkY=; fh=sS+J4OyOC0EcVLWJpS3mBHGeO+0+dYZJ+ImCUfzsrH4=; b=BGnNLySLmatB2mYF8U8vdmr1zNn4Db30cz+j/6qNdB3eSPlKL5hOIcbU9eBaPRDXg5 n1p0VqrRYW04BLv305cGcp/ueFZmDjBD34cSjCUN3O5Au2sZq2Py6WkYaUfDaNhRi1TV a4n5NpCv4xaKXL6B+mhKghhqB8Li8w3QH0O2w2Vd3NPrcBD4tmSLQ9CvMcaJRWDoVYOO gpoNWJ8g7bc+Oeo1XgCuEBELer2/1sSpllZmrQiiWx0mO8X8qbNqTVXUonmsT9OUUYmc it1KBDeAaQjR09NUuqJdLbDpEXo0ft7bR/OQ8/9larcfexhmQQBM1M7bR2XAKnj7SEVq yeJQ== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.33 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from lipwig.vger.email (lipwig.vger.email. [23.128.96.33]) by mx.google.com with ESMTPS id 127-20020a630985000000b005be0028c5easi8504082pgj.401.2023.12.04.15.49.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 Dec 2023 15:49:43 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.33 as permitted sender) client-ip=23.128.96.33; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.33 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by lipwig.vger.email (Postfix) with ESMTP id 33D11804C6FB; Mon, 4 Dec 2023 15:49:34 -0800 (PST) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.11 at lipwig.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343526AbjLDXtT (ORCPT + 99 others); Mon, 4 Dec 2023 18:49:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45288 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234754AbjLDXtP (ORCPT ); Mon, 4 Dec 2023 18:49:15 -0500 Received: from 66-220-144-178.mail-mxout.facebook.com (66-220-144-178.mail-mxout.facebook.com [66.220.144.178]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6F6B0FA for ; Mon, 4 Dec 2023 15:49:21 -0800 (PST) Received: by devbig1114.prn1.facebook.com (Postfix, from userid 425415) id E345C105D3A87; Mon, 4 Dec 2023 15:49:09 -0800 (PST) From: Stefan Roesch To: kernel-team@fb.com Cc: shr@devkernel.io, akpm@linux-foundation.org, david@redhat.com, hannes@cmpxchg.org, riel@surriel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v3 2/4] mm/ksm: add sysfs knobs for advisor Date: Mon, 4 Dec 2023 15:49:04 -0800 Message-Id: <20231204234906.1237478-3-shr@devkernel.io> X-Mailer: git-send-email 2.39.3 In-Reply-To: <20231204234906.1237478-1-shr@devkernel.io> References: <20231204234906.1237478-1-shr@devkernel.io> MIME-Version: 1.0 X-Spam-Status: No, score=-0.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lipwig.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (lipwig.vger.email [0.0.0.0]); Mon, 04 Dec 2023 15:49:34 -0800 (PST) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1784397203947838129 X-GMAIL-MSGID: 1784397203947838129 This adds four new knobs for the KSM advisor to influence its behaviour. The knobs are: - advisor_mode: none: no advisor (default) scan-time: scan time advisor - advisor_max_cpu: 70 (default, cpu usage percent) - advisor_min_pages: 500 (default) - advisor_max_pages: 30000 (default) - advisor_target_scan_time: 200 (default in seconds) The new values will take effect on the next scan round. Signed-off-by: Stefan Roesch --- mm/ksm.c | 127 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 127 insertions(+) diff --git a/mm/ksm.c b/mm/ksm.c index b27010fa2e946..18b7185bbc65b 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -3735,6 +3735,128 @@ static ssize_t smart_scan_store(struct kobject *kobj, } KSM_ATTR(smart_scan); +static ssize_t advisor_mode_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + const char *output; + + if (ksm_advisor == KSM_ADVISOR_NONE) + output = "[none] scan-time"; + else if (ksm_advisor == KSM_ADVISOR_SCAN_TIME) + output = "none [scan-time]"; + + return sysfs_emit(buf, "%s\n", output); +} + +static ssize_t advisor_mode_store(struct kobject *kobj, + struct kobj_attribute *attr, const char *buf, + size_t count) +{ + if (sysfs_streq("scan-time", buf)) + ksm_advisor = KSM_ADVISOR_SCAN_TIME; + else if (sysfs_streq("none", buf)) + ksm_advisor = KSM_ADVISOR_NONE; + else + return -EINVAL; + + /* Set advisor default values */ + init_advisor(); + set_advisor_defaults(); + + return count; +} +KSM_ATTR(advisor_mode); + +static ssize_t advisor_max_cpu_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sysfs_emit(buf, "%u\n", ksm_advisor_max_cpu); +} + +static ssize_t advisor_max_cpu_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + int err; + unsigned long value; + + err = kstrtoul(buf, 10, &value); + if (err) + return -EINVAL; + + ksm_advisor_max_cpu = value; + return count; +} +KSM_ATTR(advisor_max_cpu); + +static ssize_t advisor_min_pages_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sysfs_emit(buf, "%lu\n", ksm_advisor_min_pages); +} + +static ssize_t advisor_min_pages_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + int err; + unsigned long value; + + err = kstrtoul(buf, 10, &value); + if (err) + return -EINVAL; + + ksm_advisor_min_pages = value; + return count; +} +KSM_ATTR(advisor_min_pages); + +static ssize_t advisor_max_pages_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sysfs_emit(buf, "%lu\n", ksm_advisor_max_pages); +} + +static ssize_t advisor_max_pages_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + int err; + unsigned long value; + + err = kstrtoul(buf, 10, &value); + if (err) + return -EINVAL; + + ksm_advisor_max_pages = value; + return count; +} +KSM_ATTR(advisor_max_pages); + +static ssize_t advisor_target_scan_time_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sysfs_emit(buf, "%lu\n", ksm_advisor_target_scan_time); +} + +static ssize_t advisor_target_scan_time_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + int err; + unsigned long value; + + err = kstrtoul(buf, 10, &value); + if (err) + return -EINVAL; + if (value < 1) + return -EINVAL; + + ksm_advisor_target_scan_time = value; + return count; +} +KSM_ATTR(advisor_target_scan_time); + static struct attribute *ksm_attrs[] = { &sleep_millisecs_attr.attr, &pages_to_scan_attr.attr, @@ -3757,6 +3879,11 @@ static struct attribute *ksm_attrs[] = { &use_zero_pages_attr.attr, &general_profit_attr.attr, &smart_scan_attr.attr, + &advisor_mode_attr.attr, + &advisor_max_cpu_attr.attr, + &advisor_min_pages_attr.attr, + &advisor_max_pages_attr.attr, + &advisor_target_scan_time_attr.attr, NULL, }; From patchwork Mon Dec 4 23:49:05 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Roesch X-Patchwork-Id: 173599 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:bcd1:0:b0:403:3b70:6f57 with SMTP id r17csp3109983vqy; Mon, 4 Dec 2023 15:49:35 -0800 (PST) X-Google-Smtp-Source: AGHT+IGhQv7hYzaIAdu/R36uIv5mMrv7uT0C6C5UKKPPH/ym/VpDsfs9qh80p48J3ntI4YbuKUZE X-Received: by 2002:a05:6808:192:b0:3b8:b063:9b7d with SMTP id w18-20020a056808019200b003b8b0639b7dmr4520146oic.111.1701733774902; Mon, 04 Dec 2023 15:49:34 -0800 (PST) ARC-Seal: i=1; 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[2620:137:e000::3:1]) by mx.google.com with ESMTPS id s21-20020a63d055000000b005be3c09abf1si8581940pgi.397.2023.12.04.15.49.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 Dec 2023 15:49:34 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:1 as permitted sender) client-ip=2620:137:e000::3:1; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:1 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by morse.vger.email (Postfix) with ESMTP id 6CCB080227C2; Mon, 4 Dec 2023 15:49:30 -0800 (PST) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.11 at morse.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343494AbjLDXtQ (ORCPT + 99 others); Mon, 4 Dec 2023 18:49:16 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45282 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234721AbjLDXtP (ORCPT ); Mon, 4 Dec 2023 18:49:15 -0500 Received: from 66-220-144-178.mail-mxout.facebook.com (66-220-144-178.mail-mxout.facebook.com [66.220.144.178]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AFA6F101 for ; Mon, 4 Dec 2023 15:49:21 -0800 (PST) Received: by devbig1114.prn1.facebook.com (Postfix, from userid 425415) id EF772105D3A8A; Mon, 4 Dec 2023 15:49:09 -0800 (PST) From: Stefan Roesch To: kernel-team@fb.com Cc: shr@devkernel.io, akpm@linux-foundation.org, david@redhat.com, hannes@cmpxchg.org, riel@surriel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v3 3/4] mm/ksm: add tracepoint for ksm advisor Date: Mon, 4 Dec 2023 15:49:05 -0800 Message-Id: <20231204234906.1237478-4-shr@devkernel.io> X-Mailer: git-send-email 2.39.3 In-Reply-To: <20231204234906.1237478-1-shr@devkernel.io> References: <20231204234906.1237478-1-shr@devkernel.io> MIME-Version: 1.0 X-Spam-Status: No, score=-0.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on morse.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (morse.vger.email [0.0.0.0]); Mon, 04 Dec 2023 15:49:30 -0800 (PST) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1784397194859404009 X-GMAIL-MSGID: 1784397194859404009 This adds a new tracepoint for the ksm advisor. It reports the last scan time, the new setting of the pages_to_scan parameter and the average cpu percent usage of the ksmd background thread for the last scan. Signed-off-by: Stefan Roesch Acked-by: David Hildenbrand --- include/trace/events/ksm.h | 33 +++++++++++++++++++++++++++++++++ mm/ksm.c | 1 + 2 files changed, 34 insertions(+) diff --git a/include/trace/events/ksm.h b/include/trace/events/ksm.h index b5ac35c1d0e88..e728647b5d268 100644 --- a/include/trace/events/ksm.h +++ b/include/trace/events/ksm.h @@ -245,6 +245,39 @@ TRACE_EVENT(ksm_remove_rmap_item, __entry->pfn, __entry->rmap_item, __entry->mm) ); +/** + * ksm_advisor - called after the advisor has run + * + * @scan_time: scan time in seconds + * @pages_to_scan: new pages_to_scan value + * @cpu_percent: cpu usage in percent + * + * Allows to trace the ksm advisor. + */ +TRACE_EVENT(ksm_advisor, + + TP_PROTO(s64 scan_time, unsigned long pages_to_scan, + unsigned int cpu_percent), + + TP_ARGS(scan_time, pages_to_scan, cpu_percent), + + TP_STRUCT__entry( + __field(s64, scan_time) + __field(unsigned long, pages_to_scan) + __field(unsigned int, cpu_percent) + ), + + TP_fast_assign( + __entry->scan_time = scan_time; + __entry->pages_to_scan = pages_to_scan; + __entry->cpu_percent = cpu_percent; + ), + + TP_printk("ksm scan time %lld pages_to_scan %lu cpu percent %u", + __entry->scan_time, __entry->pages_to_scan, + __entry->cpu_percent) +); + #endif /* _TRACE_KSM_H */ /* This part must be outside protection */ diff --git a/mm/ksm.c b/mm/ksm.c index 18b7185bbc65b..b8065c5d5f833 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -455,6 +455,7 @@ static void scan_time_advisor(void) advisor_ctx.cpu_time = cpu_time; ksm_thread_pages_to_scan = pages; + trace_ksm_advisor(scan_time, pages, cpu_percent); } static void run_advisor(void) From patchwork Mon Dec 4 23:49:06 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Roesch X-Patchwork-Id: 173602 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:bcd1:0:b0:403:3b70:6f57 with SMTP id r17csp3110432vqy; Mon, 4 Dec 2023 15:50:49 -0800 (PST) X-Google-Smtp-Source: AGHT+IHvNicjwrWNlelB4KXVX7AGMTGpLzS4cG0XxuKiMy0FbqYka1YkaTZEdzAVol0rMG9zRV9m X-Received: by 2002:a17:90b:17c7:b0:285:b6a6:c40b with SMTP id me7-20020a17090b17c700b00285b6a6c40bmr339832pjb.42.1701733848718; Mon, 04 Dec 2023 15:50:48 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1701733848; cv=none; d=google.com; s=arc-20160816; b=o/3OJ7MJahrXcPjA4D5W+BQ1nFY9LuIeO3XwWHLh61FL8PuyPl0LZKGsRuZ3ydfUqK Cu0ouQ8/rb1HcUBOE2ZrBUPC41EYLSIQOW+KbtciV5Ip2OONAfsUgt/ORh1AIyxIMO79 kl7SgQjpZ9e1tOPs/BmtP4AfGGCxlMS/5BPPOLMFRhi6JI6HURGvC4CWokt905VtakpZ 42LGf61X88v+JCX3LBu1JFxGWvYd60EeyUvl7u+XEbXRXgqvITzbut3b9U7mRXcgtig2 vKZM9QziOO/LSOPnHB+TUFxTriH11BRFTDxzo7j2FkfzAoRCn1A6ZfT7sEC0u9uNPVwP 18gg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from; bh=LZorcygG4jZkuFwNCG5i1dAxxLHjOAqJDWOY87GS9rg=; fh=sS+J4OyOC0EcVLWJpS3mBHGeO+0+dYZJ+ImCUfzsrH4=; b=XMD7I6IM91LhIbhHxDP2j9bS2nhGv2vZp3V54PnlAqhOZt1rnMAUKeLL2z/5NmGXoZ +uohQStCAAM5rg9n6RETozBu7393q+mMOxbwi3CLDBwz0h3bQp6Q+5fmBRVfNKKH5Ryz iVb7OuO7fExP37z5vvC8JpZSJ7yXeNePUlWzBp468Aq+fVrWLqqaPZAcXbTdhkcbJtTU J5aGHFzyDMuPwfb61wq3Mv+Jt/aRnq4lYFj7Vqxiz67VAFp/bdyfn+blQaggyWukxjMp OcqCExCz6o5M550lBq8xFb8OO1pyRvXfK3QJx9cpGB1D6pajpxG0bkySQ3Z0SfDnuAz+ TxSw== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:6 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from pete.vger.email (pete.vger.email. [2620:137:e000::3:6]) by mx.google.com with ESMTPS id j5-20020a170902da8500b001cfc170c11asi1806815plx.475.2023.12.04.15.50.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 Dec 2023 15:50:48 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:6 as permitted sender) client-ip=2620:137:e000::3:6; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:6 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by pete.vger.email (Postfix) with ESMTP id EDE5B8097A61; Mon, 4 Dec 2023 15:50:19 -0800 (PST) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.11 at pete.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343583AbjLDXtV (ORCPT + 99 others); Mon, 4 Dec 2023 18:49:21 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45304 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234764AbjLDXtP (ORCPT ); Mon, 4 Dec 2023 18:49:15 -0500 Received: from 66-220-144-178.mail-mxout.facebook.com (66-220-144-178.mail-mxout.facebook.com [66.220.144.178]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C0C43102 for ; Mon, 4 Dec 2023 15:49:21 -0800 (PST) Received: by devbig1114.prn1.facebook.com (Postfix, from userid 425415) id 057BB105D3A8C; Mon, 4 Dec 2023 15:49:09 -0800 (PST) From: Stefan Roesch To: kernel-team@fb.com Cc: shr@devkernel.io, akpm@linux-foundation.org, david@redhat.com, hannes@cmpxchg.org, riel@surriel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v3 4/4] mm/ksm: document ksm advisor and its sysfs knobs Date: Mon, 4 Dec 2023 15:49:06 -0800 Message-Id: <20231204234906.1237478-5-shr@devkernel.io> X-Mailer: git-send-email 2.39.3 In-Reply-To: <20231204234906.1237478-1-shr@devkernel.io> References: <20231204234906.1237478-1-shr@devkernel.io> MIME-Version: 1.0 X-Spam-Status: No, score=-0.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on pete.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (pete.vger.email [0.0.0.0]); Mon, 04 Dec 2023 15:50:20 -0800 (PST) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1784397272145393605 X-GMAIL-MSGID: 1784397272145393605 This documents the KSM advisor and its new knobs in /sys/fs/kernel/mm. Signed-off-by: Stefan Roesch Acked-by: David Hildenbrand --- Documentation/admin-guide/mm/ksm.rst | 54 ++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) diff --git a/Documentation/admin-guide/mm/ksm.rst b/Documentation/admin-guide/mm/ksm.rst index e59231ac6bb71..297c4a0d04dee 100644 --- a/Documentation/admin-guide/mm/ksm.rst +++ b/Documentation/admin-guide/mm/ksm.rst @@ -80,6 +80,9 @@ pages_to_scan how many pages to scan before ksmd goes to sleep e.g. ``echo 100 > /sys/kernel/mm/ksm/pages_to_scan``. + The pages_to_scan value cannot be changed if ``advisor_mode`` has + been set to scan-time. + Default: 100 (chosen for demonstration purposes) sleep_millisecs @@ -164,6 +167,29 @@ smart_scan optimization is enabled. The ``pages_skipped`` metric shows how effective the setting is. +advisor_mode + The ``advisor_mode`` selects the current advisor. Two modes are + supported: none and scan-time. The default is none. By setting + ``advisor_mode`` to scan-time, the scan time advisor is enabled. + The section about ``advisor`` explains in detail how the scan time + advisor works. + +adivsor_max_cpu + specifies the upper limit of the cpu percent usage of the ksmd + background thread. The default is 70. + +advisor_target_scan_time + specifies the target scan time in seconds to scan all the candidate + pages. The default value is 200 seconds. + +advisor_min_pages + specifies the lower limit of the ``pages_to_scan`` parameter of the + scan time advisor. The default is 500. + +adivsor_max_pages + specifies the upper limit of the ``pages_to_scan`` parameter of the + scan time advisor. The default is 30000. + The effectiveness of KSM and MADV_MERGEABLE is shown in ``/sys/kernel/mm/ksm/``: general_profit @@ -263,6 +289,34 @@ ksm_swpin_copy note that KSM page might be copied when swapping in because do_swap_page() cannot do all the locking needed to reconstitute a cross-anon_vma KSM page. +Advisor +======= + +The number of candidate pages for KSM is dynamic. It can be often observed +that during the startup of an application more candidate pages need to be +processed. Without an advisor the ``pages_to_scan`` parameter needs to be +sized for the maximum number of candidate pages. The scan time advisor can +changes the ``pages_to_scan`` parameter based on demand. + +The advisor can be enabled, so KSM can automatically adapt to changes in the +number of candidate pages to scan. Two advisors are implemented: none and +scan-time. With none, no advisor is enabled. The default is none. + +The scan time advisor changes the ``pages_to_scan`` parameter based on the +observed scan times. The possible values for the ``pages_to_scan`` parameter is +limited by the ``advisor_max_cpu`` parameter. In addition there is also the +``advisor_target_scan_time`` parameter. This parameter sets the target time to +scan all the KSM candidate pages. The parameter ``advisor_target_scan_time`` +decides how aggressive the scan time advisor scans candidate pages. Lower +values make the scan time advisor to scan more aggresively. This is the most +important parameter for the configuration of the scan time advisor. + +The initial value and the maximum value can be changed with ``advisor_min_pages`` +and ``advisor_max_pages``. The default values are sufficient for most workloads. + +The ``pages_to_scan`` parameter is re-calculated after a scan has been completed. + + -- Izik Eidus, Hugh Dickins, 17 Nov 2009