From: Steven Rostedt <rostedt@goodmis.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>,
David Stevens <stevensd@google.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Thomas Gleixner <tglx@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
Andrew Morton <akpm@linux-foundation.org>,
Dave Chinner <david@fromorbit.com>, Qi Zheng <qi.zheng@linux.dev>,
Roman Gushchin <roman.gushchin@linux.dev>,
Muchun Song <muchun.song@linux.dev>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Valentin Schneider <vschneid@redhat.com>,
K Prateek Nayak <kprateek.nayak@amd.com>,
Uladzislau Rezki <urezki@gmail.com>,
David Hildenbrand <david@kernel.org>,
Lorenzo Stoakes <ljs@kernel.org>,
"Liam R . Howlett" <liam@infradead.org>,
Vlastimil Babka <vbabka@kernel.org>,
Mike Rapoport <rppt@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>, Kees Cook <kees@kernel.org>,
Clark Williams <clrkwllms@kernel.org>,
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
Date: Fri, 28 Aug 2026 15:17:47 -0400 [thread overview]
Message-ID: <20260828151747.20035d50@gandalf.local.home> (raw)
In-Reply-To: <20260828151313.5c4a5e4b@gandalf.local.home>
On Fri, 28 Aug 2026 15:13:13 -0400
Steven Rostedt <rostedt@goodmis.org> 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
next prev parent reply other threads:[~2026-08-28 19:17 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-27 23:29 [RFC 00/10] Reclaimable kernel stacks David Stevens
2026-08-27 23:29 ` [RFC 01/10] Add !MEMCG memcg_list_lru_alloc implementation David Stevens
2026-08-27 23:29 ` [RFC 02/10] mm/vmalloc: Skip vmallocinfo NUMA stats for VM_SPARSE David Stevens
2026-08-27 23:29 ` [RFC 03/10] fork: refactor vmap stack alloc/free into helpers David Stevens
2026-08-27 23:29 ` [RFC 04/10] mm: vmalloc: support creating aligned vm areas David Stevens
2026-08-27 23:29 ` [RFC 05/10] fork: allocate reclaimable stacks with VM_SPARSE David Stevens
2026-08-27 23:29 ` [RFC 06/10] Reclaim memory from blocked kernel stacks David Stevens
2026-08-28 11:54 ` Peter Zijlstra
2026-08-28 12:01 ` Peter Zijlstra
2026-08-28 12:04 ` Peter Zijlstra
2026-08-29 0:18 ` David Stevens
2026-08-28 12:41 ` Peter Zijlstra
2026-08-28 12:57 ` Peter Zijlstra
2026-08-28 23:33 ` David Stevens
2026-08-28 13:36 ` Sebastian Andrzej Siewior
2026-08-28 13:59 ` Peter Zijlstra
2026-08-28 14:25 ` Peter Zijlstra
2026-08-28 15:58 ` Sebastian Andrzej Siewior
2026-08-28 15:10 ` Sebastian Andrzej Siewior
2026-08-28 19:08 ` Steven Rostedt
2026-08-28 19:13 ` Steven Rostedt
2026-08-28 19:17 ` Steven Rostedt [this message]
2026-08-28 20:50 ` David Stevens
2026-08-28 21:17 ` David Stevens
2026-08-27 23:29 ` [RFC 07/10] Reclaim stacks via a shrinker David Stevens
2026-08-27 23:29 ` [RFC 08/10] Set PF_RECLAIMABLE_STACK in various places David Stevens
2026-08-28 6:33 ` K Prateek Nayak
2026-08-27 23:29 ` [RFC 09/10] x86: Enable reclaimable stacks David Stevens
2026-08-27 23:29 ` [RFC 10/10] arm64: " David Stevens
2026-08-28 12:47 ` [RFC 00/10] Reclaimable kernel stacks Peter Zijlstra
2026-08-28 14:33 ` Steven Rostedt
2026-08-28 14:35 ` Peter Zijlstra
2026-08-28 14:45 ` Peter Zijlstra
2026-08-28 16:10 ` Steven Rostedt
2026-08-28 17:58 ` David Stevens
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