From patchwork Thu May 15 03:01:51 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zihuan Zhang X-Patchwork-Id: 890814 Received: from mailgw.kylinos.cn (mailgw.kylinos.cn [124.126.103.232]) (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 01FBA29375F; Thu, 15 May 2025 03:04:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=124.126.103.232 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747278258; cv=none; b=osCnekwda3pSCBJpUihbGjzhYLc+qMjSjJrNmZRgeMj+4JzIGk4F+bKcGSD3qa6hXKTk10EQsb+Azxe3XTwt43Gd1Dx6D1MHOePXPawI84RPJApVfDWTE4iiebTsWY4bNkmpgNt2TKUwaxxEIdNjJZYoOS0b61n9/NQlpFAnSSI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747278258; c=relaxed/simple; bh=KbCF5MKCWNn3YP5xLgTo6/b3b/wNnyl4Ieq6Iz4mRVg=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=io+Kjl0QcRAmtmk1Q9mE++TC6iHhor2HCFZm7bUt3QkAO9XKqZNVEIqbZEUfvUXpoMvZnOgf6C2gNMyuchXGwhXlB4y5b9a3wg0CLkyWBgSPH+zsV6A96xk0BJN3vrntPsDYBKNtqJRivfmQ769KgZCdePrrEG5oqKv2d9f5m9A= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn; spf=pass smtp.mailfrom=kylinos.cn; arc=none smtp.client-ip=124.126.103.232 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kylinos.cn X-UUID: 40f45dde313911f0b29709d653e92f7d-20250515 X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.1.45, REQID:5a9b7689-c6cc-429c-bf32-1c973e39c20c, IP:0, U RL:0,TC:0,Content:0,EDM:0,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTION: release,TS:0 X-CID-META: VersionHash:6493067, CLOUDID:8860f9c49583b8e2e2cb45ee7d7b6a34, BulkI D:nil,BulkQuantity:0,Recheck:0,SF:102,TC:nil,Content:0|50,EDM:-3,IP:nil,UR L:0,File:nil,RT:nil,Bulk:nil,QS:nil,BEC:nil,COL:0,OSI:0,OSA:0,AV:0,LES:1,S PR:NO,DKR:0,DKP:0,BRR:0,BRE:0,ARC:0 X-CID-BVR: 0 X-CID-BAS: 0,_,0,_ X-CID-FACTOR: TF_CID_SPAM_SNR X-UUID: 40f45dde313911f0b29709d653e92f7d-20250515 Received: from mail.kylinos.cn [(10.44.16.175)] by mailgw.kylinos.cn (envelope-from ) (Generic MTA) with ESMTP id 606235159; Thu, 15 May 2025 11:04:02 +0800 Received: from mail.kylinos.cn (localhost [127.0.0.1]) by mail.kylinos.cn (NSMail) with SMTP id C9E55E003507; Thu, 15 May 2025 11:04:01 +0800 (CST) X-ns-mid: postfix-682559A1-648868357 Received: from localhost.localdomain (unknown [172.25.120.24]) by mail.kylinos.cn (NSMail) with ESMTPA id 4EB96E003506; Thu, 15 May 2025 11:04:01 +0800 (CST) From: Zihuan Zhang To: rafael@kernel.org, pavel@kernel.org Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Zihuan Zhang Subject: [PATCH v1] freezer: Skip zombie processes early to reduce lock contention Date: Thu, 15 May 2025 11:01:51 +0800 Message-Id: <20250515030151.224508-1-zhangzihuan@kylinos.cn> X-Mailer: git-send-email 2.25.1 Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Currently, the freezer core processes all tasks, including zombie tasks (EXIT_ZOMBIE), when performing freeze operations. However, zombie tasks cannot be frozen since they are already dead and won't execute further. Despite this, these tasks are still passed to freeze_task(), which may involve acquiring locks and accessing unnecessary internal state. This patch introduces an early check to skip zombie tasks when calling freeze_task(), significantly reducing the lock contention, especially on systems with many short-lived processes or a high volume of process exits. Benefits: - Reduces unnecessary lock contention by skipping zombie processes earlier in the freeze process. - Improves overall freezing performance, particularly in high-load systems where there are many zombie processes. Signed-off-by: Zihuan Zhang --- kernel/freezer.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/freezer.c b/kernel/freezer.c index 8d530d0949ff..a6867195bb77 100644 --- a/kernel/freezer.c +++ b/kernel/freezer.c @@ -164,6 +164,9 @@ bool freeze_task(struct task_struct *p) { unsigned long flags; + if (p->exit_state == EXIT_ZOMBIE) + return false; + spin_lock_irqsave(&freezer_lock, flags); if (!freezing(p) || frozen(p) || __freeze_task(p)) { spin_unlock_irqrestore(&freezer_lock, flags); @@ -203,6 +206,9 @@ void __thaw_task(struct task_struct *p) { unsigned long flags; + if (p->exit_state == EXIT_ZOMBIE) + return; + spin_lock_irqsave(&freezer_lock, flags); if (WARN_ON_ONCE(freezing(p))) goto unlock;