From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-174.mta0.migadu.com (out-174.mta0.migadu.com [91.218.175.174]) (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 107E437BE8D for ; Wed, 10 Jun 2026 19:53:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.174 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781121195; cv=none; b=l+IYHShKHsvdwOusvqfdy91HW6YcqPoLv/zILwIwZ+Q6jyBQACVwSyBb+WFVP+Z++/gUr6tSgkZxapvXcyShBUBmLiGlCpb1J9OQcRSylwqu4xkyXUiA4L2H9fprKVzxLuxo3BvXwLDRd6/0mlVfeoHKBVcYgmvuWTu8MBXbF/g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781121195; c=relaxed/simple; bh=PdA92GaxC2iI5xrbQDhqtPgsCnUzs7qU2yK9O87omuc=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=FrIj4jlz0l7tViha1IB8KXa/vMTtT0uSgWYy6TBD6B0UVQd/DymLHR582HHXQYzMZ1fEd7eMeGJFoqYZ+VroczSn623qAZPjEUQvjVqpCDil8db8ufxqVDxHu0CWKOXuDxIowJPSIJBEWxMOFM9b6cLYpV1U9DpCAfCqDVEFMVE= 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=KIT1SxJv; arc=none smtp.client-ip=91.218.175.174 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="KIT1SxJv" 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=1781121180; 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=fFNM+csKuGsAi8zW+tua6hmsF6Jv56ZUXMuPVDdT++g=; b=KIT1SxJvnnMM9esD4/wv1ZtvrkIc7so2MoZbLd8fD4HwqlXWLnTI1+chx03t1ehbZlvO7s Yb2l8RO/m2g+mbEg2u+yzJJ47onjz5+Z+eevu3UsW0VRqvjJ11JKxC5Wu+YlyBrOosrTTO hyNY3tLcrojL03mL86KA6EMszoCnHmQ= 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 v3] mm/lruvec: trace LRU add drains and drain-all requests Date: Wed, 10 Jun 2026 12:52:20 -0700 Message-ID: <20260610195220.12403-1-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_add_drain_all to capture callers of __lru_add_drain_all and whether they set the force flag for all CPUs. The tracepoint resembles the signature of the enclosing function, but is needed because of potential inlining. Signed-off-by: JP Kobryn --- include/trace/events/pagemap.h | 37 ++++++++++++++++++++++++++++++++++ mm/swap.c | 7 ++++++- 2 files changed, 43 insertions(+), 1 deletion(-) diff --git a/include/trace/events/pagemap.h b/include/trace/events/pagemap.h index 171524d3526d..ff3da07ccb40 100644 --- a/include/trace/events/pagemap.h +++ b/include/trace/events/pagemap.h @@ -77,6 +77,43 @@ 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_add_drain_all, + + TP_PROTO(bool force_all_cpus), + + TP_ARGS(force_all_cpus), + + TP_STRUCT__entry( + __field(bool, force_all_cpus ) + ), + + TP_fast_assign( + __entry->force_all_cpus = force_all_cpus; + ), + + TP_printk("force_all_cpus=%s", + __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..e14b7612f896 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. */ @@ -869,6 +872,8 @@ static inline void __lru_add_drain_all(bool force_all_cpus) if (WARN_ON(!mm_percpu_wq)) return; + trace_mm_lru_add_drain_all(force_all_cpus); + /* * Guarantee folio_batch counter stores visible by this CPU * are visible to other CPUs before loading the current drain -- 2.54.0