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[34.150.221.228]) by smtp.gmail.com with ESMTPSA id x8-20020a05620a258800b006b9a89d408csm4377123qko.100.2022.08.19.13.49.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Aug 2022 13:49:06 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , paulmck@kernel.org, Rushikesh S Kadam , "Uladzislau Rezki (Sony)" , Neeraj upadhyay , Frederic Weisbecker , Steven Rostedt , rcu , vineeth@bitbyteword.org Subject: [PATCH v4 03/14] rcuscale: Add laziness and kfree tests Date: Fri, 19 Aug 2022 20:48:46 +0000 Message-Id: <20220819204857.3066329-4-joel@joelfernandes.org> X-Mailer: git-send-email 2.37.2.609.g9ff673ca1a-goog In-Reply-To: <20220819204857.3066329-1-joel@joelfernandes.org> References: <20220819204857.3066329-1-joel@joelfernandes.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org We aad 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_lazy() and check memory pressure. In my testing, call_rcu_lazy() does well to keep memory pressure under control, similar to kfree_rcu(). Signed-off-by: Joel Fernandes (Google) --- kernel/rcu/rcuscale.c | 74 ++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 73 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c index 277a5bfb37d4..ed5544227f4d 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_rcu_by_lazy, 0, "Use call_rcu_lazy() to emulate kfree_rcu()?"); static char *scale_type = "rcu"; module_param(scale_type, charp, 0444); @@ -658,6 +659,14 @@ struct kfree_obj { struct rcu_head rh; }; +/* Used if doing RCU-kfree'ing via call_rcu_lazy(). */ +static void kfree_rcu_lazy(struct rcu_head *rh) +{ + struct kfree_obj *obj = container_of(rh, struct kfree_obj, rh); + + kfree(obj); +} + static int kfree_scale_thread(void *arg) { @@ -695,6 +704,11 @@ kfree_scale_thread(void *arg) if (!alloc_ptr) return -ENOMEM; + if (kfree_rcu_by_lazy) { + call_rcu_lazy(&(alloc_ptr->rh), kfree_rcu_lazy); + 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 @@ -737,6 +751,9 @@ kfree_scale_cleanup(void) { int i; + if (kfree_rcu_by_lazy) + rcu_force_call_rcu_to_lazy(false); + if (torture_cleanup_begin()) return; @@ -766,11 +783,64 @@ kfree_scale_shutdown(void *arg) return -EINVAL; } +// Used if doing RCU-kfree'ing via call_rcu_lazy(). +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; + unsigned long orig_jif, jif_start; + + // If lazy-rcu based kfree'ing is requested, then for kernels that + // support it, force all call_rcu() to call_rcu_lazy() so that non-lazy + // CBs do not remove laziness of the lazy ones (since the test tries to + // stress call_rcu_lazy() for OOM). + // + // Also, do a quick self-test to ensure laziness is as much as + // expected. + if (kfree_rcu_by_lazy && !IS_ENABLED(CONFIG_RCU_LAZY)) { + pr_alert("CONFIG_RCU_LAZY is disabled, falling back to kfree_rcu() " + "for delayed RCU kfree'ing\n"); + kfree_rcu_by_lazy = 0; + } + + if (kfree_rcu_by_lazy) { + /* do a test to check the timeout. */ + orig_jif = rcu_lazy_get_jiffies_till_flush(); + + rcu_force_call_rcu_to_lazy(true); + rcu_lazy_set_jiffies_till_flush(2 * HZ); + rcu_barrier(); + + jif_start = jiffies; + jiffies_at_lazy_cb = 0; + call_rcu_lazy(&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: Lazy 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: Lazy CBs are being too lazy!\n"); + WARN_ON_ONCE(1); + return -1; + } + } kfree_nrealthreads = compute_real(kfree_nthreads); /* Start up the kthreads. */ @@ -783,7 +853,9 @@ 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_rcu_by_lazy=%d\n", + kfree_mult * sizeof(struct kfree_obj), + kfree_rcu_by_lazy); kfree_reader_tasks = kcalloc(kfree_nrealthreads, sizeof(kfree_reader_tasks[0]), GFP_KERNEL);