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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A9648C61DBD for ; Fri, 28 Aug 2026 19:17:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To:Message-ID:Subject:Cc:To: From:Date:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=0RDwr71FlsrAMrAAlqln64IM9QGsxwXWA77DtZDfZwQ=; b=iIr8E1y530rnbN5yckVlvRlljY a4lEClPymMyDPKOYvg6zGlWUXZRrAz+MGpQZY4Vm0GHfY3i0jq3tOBkCHelu+CRkZcsqcGvxPLqW0 ucY8smTwq3vjmm+XaZXfGeEHYdGAvsn+pq9JfWO8d1zSOMvzSjkWK+71zdCRw7fH5gWAOsxGXqBvA 3EZgThnqqS/h7Nxam8U/s8tYyOdDiXda+II5Fqgk1yNX1AJX4OlY2+XeboiXxaCoOJUbSp3wN69mw c+WPZP6xp/Do9vYjHq68oDRQNyl9M6H7HMq3xjpOjAs3pZ4dPp4gIekRAL2yrJdqMYKESlt1Cjf+I zz9jaRKQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x024h-00000006LVU-3vd9; Fri, 28 Aug 2026 19:17:15 +0000 Received: from smtprelay0015.hostedemail.com ([216.40.44.15] helo=relay.hostedemail.com) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x024e-00000006LUv-2dSS for linux-arm-kernel@lists.infradead.org; Fri, 28 Aug 2026 19:17:13 +0000 Received: from omf05.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id C52951A053F; Fri, 28 Aug 2026 19:17:06 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf05.hostedemail.com (Postfix) with ESMTPA id C3E9F20011; Fri, 28 Aug 2026 19:16:57 +0000 (UTC) Date: Fri, 28 Aug 2026 15:17:47 -0400 From: Steven Rostedt To: Sebastian Andrzej Siewior Cc: Peter Zijlstra , David Stevens , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H . Peter Anvin" , Andrew Morton , Dave Chinner , Qi Zheng , Roman Gushchin , Muchun Song , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Uladzislau Rezki , David Hildenbrand , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Clark Williams , suleiman@google.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-rt-devel@lists.linux.dev Subject: Re: [RFC 06/10] Reclaim memory from blocked kernel stacks Message-ID: <20260828151747.20035d50@gandalf.local.home> In-Reply-To: <20260828151313.5c4a5e4b@gandalf.local.home> References: <20260827232948.2520558-1-stevensd@google.com> <20260827232948.2520558-7-stevensd@google.com> <20260828133620._x2XfJR_@linutronix.de> <20260828135947.GU776954@noisy.programming.kicks-ass.net> <20260828151018.HnR9xV1N@linutronix.de> <20260828150836.2d5b378c@gandalf.local.home> <20260828151313.5c4a5e4b@gandalf.local.home> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: C3E9F20011 X-Stat-Signature: j65tfsnn7wb96ijjjfomjeapo6aro4m7 X-Rspamd-Server: rspamout03 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX1/FRCRqi3s+JC4roW7NUQua3g10tn9P4XM= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=goodmis.org; h=date:from:to:cc:subject:message-id:in-reply-to:references:mime-version:content-type:content-transfer-encoding; s=dkim1; bh=0RDwr71FlsrAMrAAlqln64IM9QGsxwXWA77DtZDfZwQ=; b=gAZTVjGDveN8fhsH4aJV2blL0f0S/QpEEvr3BQpYaHupiEQdLMD69nFOfdLEk1spL0/g6lXtTnfNyIqHZGTSM2GCgE4DvzYvzij8bAWlZRrSpkm67+yI+NJTg387b0JmME/jtx2tEqWIUYUrCD2W7DFVoX4NatssuHtJiesq2nE= X-HE-Tag: 1787944617-357454 X-HE-Meta: U2FsdGVkX1+ViF3OvOgaM5ssQLR7tn0uySWJaFHYtcXWZ21cz7nnxMRW6iHpDWrp6Htrs0cIkgW4SbBQGFpZUf1ROkYnZEWGOtcWKXjDukDAh5xQHzSUkPxJbyaumnTpSqP3YXkkCipkNohafMlloaOqbdI5ACVjC77j7iGbrpU8lCltcFJhtONUqXBCJpw9eTajIr0/aLHn6NisdoeErwIxVK/oB2Np5iYGqcWQEGRVIxOt9i1N8E1VkhWj8uFuSoYqfpNN0eEmhPs7aE8vmz2WPbGl+v4Ry92BAG7LkkOQAqWIZjLFKEu432FqDcWspoc2zzLFnstcV5vVdG65ka7IObsOxeMhd+5KlkygWN4xwraefOr4pQuVKgzS9Rrd X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260828_121712_741296_0F889E0D X-CRM114-Status: UNSURE ( 9.87 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, 28 Aug 2026 15:13:13 -0400 Steven Rostedt wrote: > If one worries about stack size, they may want to turn off > CONFIG_RANDOMIZE_KSTACK_OFFSET as I see some big numbers for do_syscall_64() And the scheduler has some heavy stack usage here! # trace-cmd stack (stack tracer running) Depth Size Location (31 entries) ----- ---- -------- 0) 8120 48 __msecs_to_jiffies+0x9/0x30 1) 8072 104 update_group_capacity+0x94/0x960 2) 7968 528 update_sd_lb_stats.constprop.0+0x426/0x39b0 3) 7440 424 sched_balance_find_src_group+0x8f/0x1150 4) 7016 552 sched_balance_rq+0x934/0x4130 5) 6464 408 pick_task_fair+0xa71/0x1fe0 6) 6056 496 __schedule+0x628/0x76f0 7) 5560 32 schedule+0xde/0x2c0 8) 5528 32 io_schedule+0x8c/0x100 9) 5496 256 rq_qos_wait+0x12b/0x230 10) 5240 136 wbt_wait+0x150/0x260 11) 5104 40 __rq_qos_throttle+0x51/0xa0 12) 5064 304 blk_mq_submit_bio+0xc40/0x28e0 13) 4760 240 submit_bio_noacct_nocheck+0x410/0xb30 14) 4520 40 ext4_io_submit+0xca/0x1a0 15) 4480 144 ext4_bio_write_folio+0x5e2/0x1470 16) 4336 96 mpage_process_page_bufs+0x392/0x700 17) 4240 616 mpage_prepare_extent_to_map+0xaae/0x1120 18) 3624 480 ext4_do_writepages+0x971/0x37f0 19) 3144 312 ext4_writepages+0x2d2/0x610 20) 2832 152 do_writepages+0x21e/0x560 21) 2680 184 __writeback_single_inode+0x119/0x1240 22) 2496 752 writeback_sb_inodes+0x67d/0x17b0 23) 1744 168 __writeback_inodes_wb+0xf2/0x270 24) 1576 304 wb_writeback+0x63e/0x890 25) 1272 320 wb_workfn+0x844/0xca0 26) 952 360 process_one_work+0x8b4/0x15d0 27) 592 176 worker_thread+0x5d3/0xfb0 28) 416 64 kthread+0x33c/0x420 29) 352 160 ret_from_fork+0x65c/0x9e0 30) 192 192 ret_from_fork_asm+0x1a/0x30 Note, I'm running this on my server. That is, this is a production machine. -- Steve