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 DD150CD6E79 for ; Tue, 9 Jun 2026 04:12:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 282326B0005; Tue, 9 Jun 2026 00:12:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 232D06B0088; Tue, 9 Jun 2026 00:12:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1218B6B008A; Tue, 9 Jun 2026 00:12:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 02F116B0005 for ; Tue, 9 Jun 2026 00:12:46 -0400 (EDT) Received: from smtpin21.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay03.hostedemail.com (Postfix) with ESMTP id A3F3BA03CA for ; Tue, 9 Jun 2026 04:12:45 +0000 (UTC) X-FDA: 84859053090.21.FC08324 Received: from out-171.mta1.migadu.com (out-171.mta1.migadu.com [95.215.58.171]) by imf17.hostedemail.com (Postfix) with ESMTP id 7ED8040005 for ; Tue, 9 Jun 2026 04:12:43 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=JZ1T1k9d; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf17.hostedemail.com: domain of jp.kobryn@linux.dev designates 95.215.58.171 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=1780978364; 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=4h6x44t/kUL5SJGKCThKAyRtoW9WrlvFmr2fXLO09kY=; b=b7a2T6Hd6K4vywthKR0qaRzb2cynl1CpECMdEl3LMsSO7BUU5aAVv8xkY9s9VHelZ+mBkB 9gxBT6x0PScZgZxg+zW6w54GPnsgRwOJdrHqxJWICQ25rEwXw4gsa4YD9nwEccWZ0zKgG/ p+NMLYgRrWKcXScgHg3WiJAd2bMWkjw= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=JZ1T1k9d; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf17.hostedemail.com: domain of jp.kobryn@linux.dev designates 95.215.58.171 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=1780978364; b=kRJd07+2k1+utLcaw10iVdqu1gnXZcSQ0n0hHYBzgxmHt2qPxmP2pUNE/afJN7AQ13rxvN aBuL7xrWlmczg1hUNpIcB1AaewXjvep11EjibMoUQteAfrIATl+hX2PyKTjpIQ2+BqoRq3 45DagG6H4p5vULwvDnQMOCIK6VSEc6Y= 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> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 7ED8040005 X-Rspam-User: X-Stat-Signature: h36uz3kte4unuyggpxcd1urwud6b8t84 X-Rspamd-Server: rspam09 X-HE-Tag: 1780978363-437643 X-HE-Meta: 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 dzcLunYS NL77sxJL31rmTYLwfMlOPYJ6UULGHoJQ9eGt33jfpSLfL6hdzOH+aTEwPAjb9lx0x7lDLIyiXmE7S1RxmGjcQA9u4n55CYPZyAc452F8jf2cf2E8mTmdvfNIGXtXvN93miw7nykQxdP1Slp2oXwbfIK6OiBZgF5WXCr3kZx3HQT5zKt3hl0YhspdYTtA4mMJhDQMo 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_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