From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-180.mta1.migadu.com (out-180.mta1.migadu.com [95.215.58.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9BE1E31E82A for ; Tue, 9 Jun 2026 04:12:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780978365; cv=none; b=IRpPMEdUbpoiPfhcOGDmaMOhdrgc+mlxp+Z4Q3TmQZKX3I5wUGfLUawC1pz6rPslxcnX+o4mkOE9tSXUSwfcaBcAyCVGeeN0QgjN3mGNODpesEI62rTG2S7aTwXAN2PPKLyaCwVGHaNDAih9CjUqIr/I7ZG7orqO+4F2Rbw/tqs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780978365; c=relaxed/simple; bh=D8oGT5zf8p6nYrA8iMJLArWNCMyBT/0Rc1Un8hcXe40=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=fekMAQNSmLMLowhb1tFeF54krGznpxK7khPehFNfM7G1NK9OkZVviAJO5OEI9LixzISJ6e6i4mDV/hyp0Li3x/nbq73lkkHUsbZLhp0K8vdgFcKBcxujSh6Ewei6/yOL6MYG4q6KiAo4DkDyjjt8d3JCa8hp2yFE+07VphPAOtY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=JZ1T1k9d; arc=none smtp.client-ip=95.215.58.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="JZ1T1k9d" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1780978361; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=4h6x44t/kUL5SJGKCThKAyRtoW9WrlvFmr2fXLO09kY=; b=JZ1T1k9dmfNfGxSCYXOE5B1BNYHUXaoBZFJM7tL5++Ew64OXoBMeebrwgAbt2wTLRUqGDP QvS/wtp+R9YSs7rg4JVmPaj+/Ev64gd+FXdmJV4LY2gNE9MRq4J9OkXPquGoTZew1+bs2l iuqJkMfsYm/i8jxh0QxrcwvENfug+D4= From: JP Kobryn To: linux-mm@kvack.org, willy@infradead.org, shakeel.butt@linux.dev, usama.arif@linux.dev, akpm@linux-foundation.org, vbabka@kernel.org, mhocko@suse.com, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, kasong@tencent.com, qi.zheng@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, chrisl@kernel.org, shikemeng@huaweicloud.com, nphamcs@gmail.com, baoquan.he@linux.dev, youngjun.park@lge.com Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: [PATCH] mm/lruvec: trace LRU add drains and drain-all queuing Date: Mon, 8 Jun 2026 21:11:56 -0700 Message-ID: <20260609041156.31127-1-jp.kobryn@linux.dev> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT LRU add batches can be drained before they reach capacity. This can be a source of LRU lock contention, but it is not currently possible to attribute these drains to callers with existing tracepoints. Add mm_lru_add_drain to report the CPU and lru_add batch count when an lru_add batch is drained. This allows tracing to distinguish full drains from partial drains and attribute them to the calling stack. Add mm_lru_drain_all_queue to report when lru_add_drain_all() queues per-CPU drain work. This captures the requester stack and target CPU for remote drain work. The event is named as a drain-all queue event because the queued work can be needed for batches other than lru_add. Signed-off-by: JP Kobryn --- include/trace/events/pagemap.h | 40 ++++++++++++++++++++++++++++++++++ mm/swap.c | 6 ++++- 2 files changed, 45 insertions(+), 1 deletion(-) diff --git a/include/trace/events/pagemap.h b/include/trace/events/pagemap.h index 171524d3526d..ea8fc46bedb0 100644 --- a/include/trace/events/pagemap.h +++ b/include/trace/events/pagemap.h @@ -77,6 +77,46 @@ TRACE_EVENT(mm_lru_activate, TP_printk("folio=%p pfn=0x%lx", __entry->folio, __entry->pfn) ); +TRACE_EVENT(mm_lru_add_drain, + + TP_PROTO(int cpu, unsigned int nr), + + TP_ARGS(cpu, nr), + + TP_STRUCT__entry( + __field(int, cpu ) + __field(unsigned int, nr ) + ), + + TP_fast_assign( + __entry->cpu = cpu; + __entry->nr = nr; + ), + + TP_printk("cpu=%d nr=%u", __entry->cpu, __entry->nr) +); + +TRACE_EVENT(mm_lru_drain_all_queue, + + TP_PROTO(int target_cpu, bool force_all_cpus), + + TP_ARGS(target_cpu, force_all_cpus), + + TP_STRUCT__entry( + __field(int, target_cpu ) + __field(bool, force_all_cpus ) + ), + + TP_fast_assign( + __entry->target_cpu = target_cpu; + __entry->force_all_cpus = force_all_cpus; + ), + + TP_printk("target_cpu=%d force_all_cpus=%s", + __entry->target_cpu, + __entry->force_all_cpus ? "true" : "false") +); + #endif /* _TRACE_PAGEMAP_H */ /* This part must be outside protection */ diff --git a/mm/swap.c b/mm/swap.c index 588f50d8f1a8..c385b93582eb 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -694,9 +694,12 @@ void lru_add_drain_cpu(int cpu) { struct cpu_fbatches *fbatches = &per_cpu(cpu_fbatches, cpu); struct folio_batch *fbatch = &fbatches->lru_add; + unsigned int nr_folios_add = folio_batch_count(fbatch); - if (folio_batch_count(fbatch)) + if (nr_folios_add) { folio_batch_move_lru(fbatch, lru_add); + trace_mm_lru_add_drain(cpu, nr_folios_add); + } fbatch = &fbatches->lru_move_tail; /* Disabling interrupts below acts as a compiler barrier. */ @@ -928,6 +931,7 @@ static inline void __lru_add_drain_all(bool force_all_cpus) if (cpu_needs_drain(cpu)) { INIT_WORK(work, lru_add_drain_per_cpu); queue_work_on(cpu, mm_percpu_wq, work); + trace_mm_lru_drain_all_queue(cpu, force_all_cpus); __cpumask_set_cpu(cpu, &has_work); } } -- 2.54.0