From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 32352CD98C7 for ; Wed, 10 Jun 2026 23:48:36 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 68DF36B0005; Wed, 10 Jun 2026 19:48:35 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 63EBE6B0088; Wed, 10 Jun 2026 19:48:35 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 52DAC6B008C; Wed, 10 Jun 2026 19:48:35 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 3EA206B0005 for ; Wed, 10 Jun 2026 19:48:35 -0400 (EDT) Received: from smtpin19.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id B9B3EC17ED for ; Wed, 10 Jun 2026 23:48:34 +0000 (UTC) X-FDA: 84865644948.19.65C797E Received: from out-176.mta1.migadu.com (out-176.mta1.migadu.com [95.215.58.176]) by imf10.hostedemail.com (Postfix) with ESMTP id 17737C0007 for ; Wed, 10 Jun 2026 23:48:32 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=spFffeka; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf10.hostedemail.com: domain of jp.kobryn@linux.dev designates 95.215.58.176 as permitted sender) smtp.mailfrom=jp.kobryn@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1781135313; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:references:dkim-signature; bh=VD+REWS2c4musML7b4GLOPUaBPQLj7UUXZPvizUGrS0=; b=4Dnk4+s4LIEGDsXEZ6p1L/dz3nn6q11YBxNgErQuRWyaLmUuQgg1H4pTOnvr4iVnbx5P9M EFTeF6C2ClSM/nfUV/II6ehYjRjUcatbTJIBR754HVfV1ev7hn6+vJ6n1MiJDWJFIERrBo tVndNjz+eprvcIzlg8EItJHUyq7UCLs= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=spFffeka; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf10.hostedemail.com: domain of jp.kobryn@linux.dev designates 95.215.58.176 as permitted sender) smtp.mailfrom=jp.kobryn@linux.dev ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1781135313; b=NFH5dJQLrHwclYZ648Pt/XtLSKNweWhXZS3UKwU3spl8tsdhywAzbFa2k3bIh1xKhcTJs7 nQ7BcPjOY8/1Du56PuvBhC8UbU+XIBGFOwQa5Aa63xPSkDOgxhoQC7mq9xLDsMfTPvXUnC iOzja/hciJFHsCn/mXhamrQOd2Z7L0o= 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=1781135310; 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=VD+REWS2c4musML7b4GLOPUaBPQLj7UUXZPvizUGrS0=; b=spFffekazjkqmDNp6yHGuellmOpBYaeh/eHvFUdl9wmedoJYjMh1XJI9OjXtllgbCMaM3I gFMk9Au1+OgRF8KOJ782m7UeSwwLad6EpeQ5Wy4gxwaIm1oKt5KmjtXPrZOn2O6j2owK+N LQ7ss6/xkKe1gAXmP2aIklOhWIZcsbs= 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 v4] mm/lruvec: trace LRU add drains and drain-all requests Date: Wed, 10 Jun 2026 16:48:08 -0700 Message-ID: <20260610234808.212397-1-jp.kobryn@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam10 X-Rspam-User: X-Stat-Signature: 6ezxi47we1a9d3hcasqpa4ar9bknfhs6 X-Rspamd-Queue-Id: 17737C0007 X-HE-Tag: 1781135312-182253 X-HE-Meta: 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 ELWwxbgo Y/2ghv52TYUiqAIWjc+2zEEUskKP1U7kraq/YzpP0uF3yg7Z2W9mhaglh1BJZEzcqhJNLliYDrV2v1UlIaClnMaG/evryLfd2FBcIpT1IKnpbqkfWNgFILUWzpj0OP9yBfgE3RNFQaGLAvbVz0GIqC2DSB6K6bqLTFHrCATPPECoRQfcoPivQgrMiWtgBbFsLKaIuI1Re5d+GkqVPD8kHXPDtY6LSQOVBdxTl Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 Reviewed-by: Barry Song Acked-by: Shakeel Butt --- v4: - renamed nr_folio_add to nr_folios in lru_add_drain() - renamed nr to nr_folios in tracepoint for consistency v3: https://lore.kernel.org/linux-mm/20260610195220.12403-1-jp.kobryn@linux.dev/ - restored and renamed tracepoint in __lru_add_drain_all v2: https://lore.kernel.org/linux-mm/20260609041156.31127-1-jp.kobryn@linux.dev/ - removed mm_lru_drain_all tracepoint v1: https://lore.kernel.org/linux-mm/20260609041156.31127-1-jp.kobryn@linux.dev/ 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..df6ac4d13dcf 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_folios), + + TP_ARGS(cpu, nr_folios), + + TP_STRUCT__entry( + __field(int, cpu ) + __field(unsigned int, nr_folios ) + ), + + TP_fast_assign( + __entry->cpu = cpu; + __entry->nr_folios = nr_folios; + ), + + TP_printk("cpu=%d nr_folios=%u", __entry->cpu, __entry->nr_folios) +); + +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..b506fa912a93 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 = folio_batch_count(fbatch); - if (folio_batch_count(fbatch)) + if (nr_folios) { folio_batch_move_lru(fbatch, lru_add); + trace_mm_lru_add_drain(cpu, nr_folios); + } 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