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Fri, 18 Jun 2021 15:19:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 838EFC43144 From: Charan Teja Reddy 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 Subject: [PATCH V4 1/3] mm: compaction: optimize proactive compaction deferrals Date: Fri, 18 Jun 2021 20:48:53 +0530 Message-Id: X-Mailer: git-send-email 2.7.4 In-Reply-To: References: In-Reply-To: References: Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=mg.codeaurora.org header.s=smtp header.b=cbHgoMpu; spf=pass (imf08.hostedemail.com: domain of bounce@mg.codeaurora.org designates 198.61.254.9 as permitted sender) smtp.mailfrom=bounce@mg.codeaurora.org; dmarc=none X-Stat-Signature: d1wmq8mc4yttyand7zq9kq9btwy5f4jf X-Rspamd-Queue-Id: 6CDD980192FE X-Rspamd-Server: rspam06 X-HE-Tag: 1624029619-182496 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 Signed-off-by: Charan Teja Reddy --- 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; } }