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From: Charan Teja Reddy <charante@codeaurora.org>
To: akpm@linux-foundation.org, vbabka@suse.cz, corbet@lwn.net,
	mcgrof@kernel.org, keescook@chromium.org, yzaikin@google.com,
	osalvador@suse.de, rientjes@google.com,
	mchehab+huawei@kernel.org, lokeshgidra@google.com,
	andrew.a.klychkov@gmail.com, xi.fengfei@h3c.com,
	nigupta@nvidia.com, dave.hansen@linux.intel.com,
	famzheng@amazon.com, mateusznosek0@gmail.com,
	oleksandr@redhat.com, sh_def@163.com
Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
	Charan Teja Reddy <charante@codeaurora.org>
Subject: [PATCH V4 1/3] mm: compaction: optimize proactive compaction deferrals
Date: Fri, 18 Jun 2021 20:48:53 +0530	[thread overview]
Message-ID: <ca4956758515acc9ad5d14198ae4022f52187336.1624028025.git.charante@codeaurora.org> (raw)
In-Reply-To: <cover.1624028025.git.charante@codeaurora.org>
In-Reply-To: <cover.1624028025.git.charante@codeaurora.org>

When fragmentation score didn't go down across the proactive compaction
i.e. when no progress is made, next wake up for proactive compaction is
deferred for 1 << COMPACT_MAX_DEFER_SHIFT(=6) times, with each wakeup
interval of HPAGE_FRAG_CHECK_INTERVAL_MSEC(=500). In each of this
wakeup, it just decrement 'proactive_defer' counter and goes sleep i.e.
it is getting woken to just decrement a counter. The same deferral time
can also achieved by simply doing the HPAGE_FRAG_CHECK_INTERVAL_MSEC <<
COMPACT_MAX_DEFER_SHIFT thus unnecessary wakeup of kcompact thread is
avoided thus also removes the need of 'proactive_defer' thread counter.

Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>
---
 Changes in V4:
  -- Removed the 'proactive_defer' thread counter by optimizing proactive
     compaction deferrals.
  -- Changes from V1 through V3 doesn't exist.

 mm/compaction.c | 29 +++++++++++++++++++----------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 84fde27..bfbcb97 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2887,7 +2887,8 @@ static int kcompactd(void *p)
 {
 	pg_data_t *pgdat = (pg_data_t *)p;
 	struct task_struct *tsk = current;
-	unsigned int proactive_defer = 0;
+	long default_timeout = msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC);
+	long timeout = default_timeout;
 
 	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
 
@@ -2904,23 +2905,30 @@ static int kcompactd(void *p)
 
 		trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
 		if (wait_event_freezable_timeout(pgdat->kcompactd_wait,
-			kcompactd_work_requested(pgdat),
-			msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC))) {
+			kcompactd_work_requested(pgdat), timeout)) {
 
 			psi_memstall_enter(&pflags);
 			kcompactd_do_work(pgdat);
 			psi_memstall_leave(&pflags);
+			/*
+			 * Reset the timeout value. The defer timeout by
+			 * proactive compaction can effectively lost
+			 * here but that is fine as the condition of the
+			 * zone changed substantionally and carrying on
+			 * with the previous defer is not useful.
+			 */
+			timeout = default_timeout;
 			continue;
 		}
 
-		/* kcompactd wait timeout */
+		/*
+		 * Start the proactive work with default timeout. Based
+		 * on the fragmentation score, this timeout is updated.
+		 */
+		timeout = default_timeout;
 		if (should_proactive_compact_node(pgdat)) {
 			unsigned int prev_score, score;
 
-			if (proactive_defer) {
-				proactive_defer--;
-				continue;
-			}
 			prev_score = fragmentation_score_node(pgdat);
 			proactive_compact_node(pgdat);
 			score = fragmentation_score_node(pgdat);
@@ -2928,8 +2936,9 @@ static int kcompactd(void *p)
 			 * Defer proactive compaction if the fragmentation
 			 * score did not go down i.e. no progress made.
 			 */
-			proactive_defer = score < prev_score ?
-					0 : 1 << COMPACT_MAX_DEFER_SHIFT;
+			if (unlikely(score >= prev_score))
+				timeout =
+				   default_timeout << COMPACT_MAX_DEFER_SHIFT;
 		}
 	}
 
-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member of the Code Aurora Forum, hosted by The Linux Foundation


  reply	other threads:[~2021-06-18 15:22 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-18 15:18 [PATCH V4,0/3] mm: compaction: proactive compaction trigger by user Charan Teja Reddy
2021-06-18 15:18 ` Charan Teja Reddy [this message]
2021-06-18 15:18 ` [PATCH V4 2/3] mm: compaction: support triggering of proactive compaction " Charan Teja Reddy
2021-06-18 15:18 ` [PATCH V4 3/3] mm: compaction: fix wakeup logic of proactive compaction Charan Teja Reddy
2021-07-03 10:22 ` [PATCH V4,0/3] mm: compaction: proactive compaction trigger by user Charan Teja Kalla
2021-07-16  4:27   ` Andrew Morton
2021-07-16 10:44     ` Charan Teja Kalla

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