From patchwork Tue Oct 11 18:01:34 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joel Fernandes X-Patchwork-Id: 13004227 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 16280C433FE for ; Tue, 11 Oct 2022 18:02:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230028AbiJKSCY (ORCPT ); Tue, 11 Oct 2022 14:02:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47698 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229925AbiJKSCR (ORCPT ); Tue, 11 Oct 2022 14:02:17 -0400 Received: from mail-qt1-x829.google.com (mail-qt1-x829.google.com [IPv6:2607:f8b0:4864:20::829]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 67E3C6BCFC for ; Tue, 11 Oct 2022 11:02:14 -0700 (PDT) Received: by mail-qt1-x829.google.com with SMTP id bb5so3413120qtb.11 for ; Tue, 11 Oct 2022 11:02:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=w4JLhz2KgqJlmd46eYLVQku/dRmLJcABiBUoXKwoaiQ=; b=ukHiI+5JsqNog8BbuT0w4hVF9+yXLHa2VRM3D+2ippceyEM4ExrVxYQx8CxWuweHrq Rnjqc/TO1srxQeB9rtVR26KcZSz637VEqzQuWsiOteHKD3WK8CXL7XDdEuMb5ftUa5FI C0OU441z5OPxFc3zn9Lzc5XBRWzTwajUH5Dko= 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 :subject:date:message-id:reply-to; bh=w4JLhz2KgqJlmd46eYLVQku/dRmLJcABiBUoXKwoaiQ=; b=3k+B8GBMVN0XS6RCHow5HMtQQI/zcpYIRZxIUZtBgp4uCkEm/nhs69WdwT92qrgZsj LzH7QDokwSUxgoFZ0/8zeqT2OG6uYzSrdfZ3H977StspvuvRUQe0KnwdYS9wocCgNIln gJ84kB6bzJmF2wsM+9RH6cGzgDUHB7W1qeMhjvSnil9O2Itrw690uMUjeTWI+Gou1qJc ji12/InZGbBeorKCtkUgP9Oqg/Ai0lyJftChbGWaorFLdNosGV9WpID93d26GGBR0Bbw l8kXriTC5v8/HhD1q3mhlgEmgsuxvreNn0RJIeVCh7lfuaTx3ZqJs6Cu6S2EVLk1VfNU DckA== X-Gm-Message-State: ACrzQf3iqZDRJswCdwJ0mp0erjLtIdp8DvsnxUMep1yzkXWW+y7gP9cw L02pnOV0XPR+0c1Ywj4ZnhKIsLca30DDtw== X-Google-Smtp-Source: AMsMyM4F7wI3rC4ZDHMgdO7PtOnGu8EEcsKY8yIVhBgzwAyyNxcyqcUij7+Ogvw0w34AXrLKLArang== X-Received: by 2002:ac8:7f48:0:b0:35b:bac4:c472 with SMTP id g8-20020ac87f48000000b0035bbac4c472mr19934504qtk.442.1665511332860; Tue, 11 Oct 2022 11:02:12 -0700 (PDT) Received: from joelboxx.c.googlers.com.com (228.221.150.34.bc.googleusercontent.com. [34.150.221.228]) by smtp.gmail.com with ESMTPSA id w22-20020a05620a425600b006cbc00db595sm13464375qko.23.2022.10.11.11.02.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Oct 2022 11:02:12 -0700 (PDT) From: "Joel Fernandes (Google)" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, rushikesh.s.kadam@intel.com, urezki@gmail.com, neeraj.iitr10@gmail.com, frederic@kernel.org, paulmck@kernel.org, rostedt@goodmis.org, youssefesmat@google.com, surenb@google.com, "Joel Fernandes (Google)" Subject: [PATCH v8 05/13] rcuscale: Add laziness and kfree tests Date: Tue, 11 Oct 2022 18:01:34 +0000 Message-Id: <20221011180142.2742289-6-joel@joelfernandes.org> X-Mailer: git-send-email 2.38.0.rc1.362.ged0d419d3c-goog In-Reply-To: <20221011180142.2742289-1-joel@joelfernandes.org> References: <20221011180142.2742289-1-joel@joelfernandes.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org We add 2 tests to rcuscale, first one is a startup test to check whether we are not too lazy or too hard working. Two, emulate kfree_rcu() itself to use call_rcu() and check memory pressure. In my testing, the new call_rcu() does well to keep memory pressure under control, similar to kfree_rcu(). Signed-off-by: Joel Fernandes (Google) --- kernel/rcu/rcuscale.c | 68 +++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 66 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c index 3ef02d4a8108..bbdcac1804ec 100644 --- a/kernel/rcu/rcuscale.c +++ b/kernel/rcu/rcuscale.c @@ -95,6 +95,7 @@ torture_param(int, verbose, 1, "Enable verbose debugging printk()s"); torture_param(int, writer_holdoff, 0, "Holdoff (us) between GPs, zero to disable"); torture_param(int, kfree_rcu_test, 0, "Do we run a kfree_rcu() scale test?"); torture_param(int, kfree_mult, 1, "Multiple of kfree_obj size to allocate."); +torture_param(int, kfree_by_call_rcu, 0, "Use call_rcu() to emulate kfree_rcu()?"); static char *scale_type = "rcu"; module_param(scale_type, charp, 0444); @@ -659,6 +660,14 @@ struct kfree_obj { struct rcu_head rh; }; +/* Used if doing RCU-kfree'ing via call_rcu(). */ +static void kfree_call_rcu(struct rcu_head *rh) +{ + struct kfree_obj *obj = container_of(rh, struct kfree_obj, rh); + + kfree(obj); +} + static int kfree_scale_thread(void *arg) { @@ -696,6 +705,11 @@ kfree_scale_thread(void *arg) if (!alloc_ptr) return -ENOMEM; + if (kfree_by_call_rcu) { + call_rcu(&(alloc_ptr->rh), kfree_call_rcu); + continue; + } + // By default kfree_rcu_test_single and kfree_rcu_test_double are // initialized to false. If both have the same value (false or true) // both are randomly tested, otherwise only the one with value true @@ -767,11 +781,59 @@ kfree_scale_shutdown(void *arg) return -EINVAL; } +// Used if doing RCU-kfree'ing via call_rcu(). +static unsigned long jiffies_at_lazy_cb; +static struct rcu_head lazy_test1_rh; +static int rcu_lazy_test1_cb_called; +static void call_rcu_lazy_test1(struct rcu_head *rh) +{ + jiffies_at_lazy_cb = jiffies; + WRITE_ONCE(rcu_lazy_test1_cb_called, 1); +} + static int __init kfree_scale_init(void) { - long i; int firsterr = 0; + long i; + unsigned long jif_start; + unsigned long orig_jif; + + // Also, do a quick self-test to ensure laziness is as much as + // expected. + if (kfree_by_call_rcu && !IS_ENABLED(CONFIG_RCU_LAZY)) { + pr_alert("CONFIG_RCU_LAZY is disabled, falling back to kfree_rcu() " + "for delayed RCU kfree'ing\n"); + kfree_by_call_rcu = 0; + } + + if (kfree_by_call_rcu) { + /* do a test to check the timeout. */ + orig_jif = rcu_lazy_get_jiffies_till_flush(); + + rcu_lazy_set_jiffies_till_flush(2 * HZ); + rcu_barrier(); + + jif_start = jiffies; + jiffies_at_lazy_cb = 0; + call_rcu(&lazy_test1_rh, call_rcu_lazy_test1); + + smp_cond_load_relaxed(&rcu_lazy_test1_cb_called, VAL == 1); + + rcu_lazy_set_jiffies_till_flush(orig_jif); + + if (WARN_ON_ONCE(jiffies_at_lazy_cb - jif_start < 2 * HZ)) { + pr_alert("ERROR: call_rcu() CBs are not being lazy as expected!\n"); + WARN_ON_ONCE(1); + return -1; + } + + if (WARN_ON_ONCE(jiffies_at_lazy_cb - jif_start > 3 * HZ)) { + pr_alert("ERROR: call_rcu() CBs are being too lazy!\n"); + WARN_ON_ONCE(1); + return -1; + } + } kfree_nrealthreads = compute_real(kfree_nthreads); /* Start up the kthreads. */ @@ -784,7 +846,9 @@ kfree_scale_init(void) schedule_timeout_uninterruptible(1); } - pr_alert("kfree object size=%zu\n", kfree_mult * sizeof(struct kfree_obj)); + pr_alert("kfree object size=%zu, kfree_by_call_rcu=%d\n", + kfree_mult * sizeof(struct kfree_obj), + kfree_by_call_rcu); kfree_reader_tasks = kcalloc(kfree_nrealthreads, sizeof(kfree_reader_tasks[0]), GFP_KERNEL);