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McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 16/17] rcutorture: Use 100ms buckets for forward-progress callback histograms Date: Sun, 11 Nov 2018 12:20:26 -0800 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20181111201956.GA11935@linux.ibm.com> References: <20181111201956.GA11935@linux.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18111120-2213-0000-0000-00000315AA56 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010028; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000270; SDB=6.01116031; UDB=6.00578740; IPR=6.00896132; MB=3.00024115; MTD=3.00000008; XFM=3.00000015; UTC=2018-11-11 20:20:34 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18111120-2214-0000-0000-00005C387AF3 Message-Id: <20181111202027.13585-16-paulmck@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-11-11_13:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=952 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1811110194 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This commit narrows the scope of each bucket of the forward-progress callback-invocation histograms from one second to 100 milliseconds, which aids debugging of forward-progress problems by making shorter-duration callback-invocation stalls visible. Signed-off-by: Paul E. McKenney --- kernel/rcu/rcutorture.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index afa98162575d..a4c4a24bdcaa 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1629,7 +1629,8 @@ static bool rcu_fwd_emergency_stop; #define MAX_FWD_CB_JIFFIES (8 * HZ) /* Maximum CB test duration. */ #define MIN_FWD_CB_LAUNDERS 3 /* This many CB invocations to count. */ #define MIN_FWD_CBS_LAUNDERED 100 /* Number of counted CBs. */ -static long n_launders_hist[2 * MAX_FWD_CB_JIFFIES / HZ]; +#define FWD_CBS_HIST_DIV 10 /* Histogram buckets/second. */ +static long n_launders_hist[2 * MAX_FWD_CB_JIFFIES / (HZ / FWD_CBS_HIST_DIV)]; static void rcu_torture_fwd_cb_hist(void) { @@ -1642,7 +1643,8 @@ static void rcu_torture_fwd_cb_hist(void) pr_alert("%s: Callback-invocation histogram (duration %lu jiffies):", __func__, jiffies - rcu_fwd_startat); for (j = 0; j <= i; j++) - pr_cont(" %ds: %ld", j + 1, n_launders_hist[j]); + pr_cont(" %ds/%d: %ld", + j + 1, FWD_CBS_HIST_DIV, n_launders_hist[j]); pr_cont("\n"); } @@ -1661,7 +1663,7 @@ static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp) rcu_fwd_cb_tail = &rfcp->rfc_next; WRITE_ONCE(*rfcpp, rfcp); WRITE_ONCE(n_launders_cb, n_launders_cb + 1); - i = ((jiffies - rcu_fwd_startat) / HZ); + i = ((jiffies - rcu_fwd_startat) / (HZ / FWD_CBS_HIST_DIV)); if (i >= ARRAY_SIZE(n_launders_hist)) i = ARRAY_SIZE(n_launders_hist) - 1; n_launders_hist[i]++; -- 2.17.1