From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Steven Rostedt <rostedt@goodmis.org>
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: Mon, 31 Aug 2026 08:55:09 +0200 [thread overview]
Message-ID: <20260831065509.qqEtERDB@linutronix.de> (raw)
In-Reply-To: <20260828151747.20035d50@gandalf.local.home>
On 2026-08-28 15:17:47 [-0400], Steven Rostedt wrote:
> 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
I didn't expect get_user_pages_unlocked() getting that big:
(stack tracer running)
Depth Size Location (60 entries)
----- ---- --------
0) 8176 48 __css_rstat_updated+0x9/0x150
1) 8128 8 __cgroup_account_cputime+0x2f/0x50
2) 8120 48 update_se+0x10c/0x1b0
3) 8072 48 update_curr+0x31/0x180
4) 8024 56 put_prev_entity+0x153/0x1f0
5) 7968 136 pick_next_task_fair+0x684/0x8e0
6) 7832 120 __schedule+0x1ca/0x1130
7) 7712 8 preempt_schedule_irq+0x38/0x60
8) 7704 72 irqentry_exit+0x148/0x6b0
9) 7632 136 asm_sysvec_apic_timer_interrupt+0x1a/0x20
10) 7496 240 HUF_compress1X_usingCTable_internal_bmi2+0x12d2/0x1c40
11) 7256 80 HUF_compress4X_usingCTable_internal+0x192/0x1d0
12) 7176 32 HUF_compressCTable_internal+0x61/0x90
13) 7144 136 HUF_compress_internal+0x2d2/0x500
14) 7008 56 HUF_compress4X_repeat+0x25/0x60
15) 6952 176 ZSTD_compressLiterals+0x1ad/0x400
16) 6776 224 ZSTD_entropyCompressSeqStore_internal+0xfb/0x320
17) 6552 112 ZSTD_compressBlock_internal+0x11b/0x210
18) 6440 296 ZSTD_compressContinue_internal+0x232/0xdd0
19) 6144 56 ZSTD_compressEnd_public+0x27/0x190
20) 6088 112 ZSTD_compressStream2+0x9fc/0xa60
21) 5976 80 ZSTD_compress2+0x83/0xd0
22) 5896 24 zstd_compress+0x3d/0x70 [zram]
23) 5872 72 zcomp_compress+0x62/0x90 [zram]
24) 5800 144 zram_submit_bio+0x558/0xb00 [zram]
25) 5656 128 __submit_bio+0x164/0x240
26) 5528 96 submit_bio_noacct_nocheck+0x134/0x390
27) 5432 64 bio_await+0xa7/0xb0
28) 5368 16 submit_bio_wait+0x16/0x20
29) 5352 184 swap_writepage_bdev_sync.isra.0+0x12e/0x230
30) 5168 40 swap_writeout+0x18d/0x2e0
31) 5128 176 shmem_writeout+0x286/0x530
32) 4952 440 shrink_folio_list+0x588/0xfc0
33) 4512 296 evict_folios+0x399/0xac0
34) 4216 160 try_to_shrink_lruvec+0x1a4/0x390
35) 4056 64 shrink_one+0xc0/0x1a0
36) 3992 240 shrink_node+0xa9a/0xcf0
37) 3752 88 do_try_to_free_pages+0xb3/0x4d0
38) 3664 176 try_to_free_pages+0xce/0x220
39) 3488 264 __alloc_pages_slowpath.constprop.0+0x8cc/0x1240
40) 3224 96 __alloc_frozen_pages_noprof+0x2f6/0x340
41) 3128 64 alloc_pages_mpol+0xb6/0x190
42) 3064 56 vma_alloc_folio_noprof+0x6e/0xd0
43) 3008 80 do_anonymous_page+0x32e/0x8f0
44) 2928 224 __handle_mm_fault+0xb31/0xf60
45) 2704 64 handle_mm_fault+0xee/0x2f0
46) 2640 152 __get_user_pages+0x1b5/0x1140
47) 2488 104 get_user_pages_unlocked+0xf0/0x330
48) 2384 128 hva_to_pfn+0x2ea/0x450 [kvm]
49) 2256 64 __kvm_faultin_pfn+0x61/0x90 [kvm]
50) 2192 120 kvm_mmu_faultin_pfn+0x2cf/0x6f0 [kvm]
51) 2072 24 kvm_tdp_page_fault+0x94/0xf0 [kvm]
52) 2048 120 kvm_mmu_do_page_fault+0x1d9/0x210 [kvm]
53) 1928 200 kvm_mmu_page_fault+0x7e/0x7b0 [kvm]
54) 1728 40 npf_interception+0xba/0x240 [kvm_amd]
55) 1688 168 kvm_arch_vcpu_ioctl_run+0x931/0x1900 [kvm]
56) 1520 200 kvm_vcpu_ioctl+0x2e4/0xa10 [kvm]
57) 1320 56 __x64_sys_ioctl+0x97/0xe0
58) 1264 1072 do_syscall_64+0xe1/0x640
59) 192 192 entry_SYSCALL_64_after_hwframe+0x76/0x7e
Does this stack tracer distinguish between the kernel-stack and
IRQ-stack? I would expect asm_sysvec_apic_timer_interrupt() on the
IRQ-stack and not adding weight to the kernel stack.
Given how close this is to 8192, I don't think two stack pages will
happen soon.
Sebastian
next prev parent reply other threads:[~2026-08-31 6:55 UTC|newest]
Thread overview: 52+ 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
2026-08-29 8:39 ` Peter Zijlstra
2026-08-29 8:43 ` Peter Zijlstra
2026-08-31 17:44 ` 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
2026-08-31 6:55 ` Sebastian Andrzej Siewior [this message]
2026-08-31 7:07 ` Peter Zijlstra
2026-08-31 15:13 ` Steven Rostedt
2026-09-01 12:32 ` Peter Zijlstra
2026-09-01 12:01 ` Will Deacon
2026-08-28 20:50 ` David Stevens
2026-08-29 8:49 ` Peter Zijlstra
2026-08-29 14:49 ` Matthew Wilcox
2026-08-31 7:14 ` Peter Zijlstra
2026-08-31 7:36 ` Sebastian Andrzej Siewior
2026-08-31 14:03 ` Vlastimil Babka (SUSE)
2026-08-31 14:19 ` Sebastian Andrzej Siewior
2026-08-28 21:17 ` David Stevens
2026-08-31 8:08 ` Sebastian Andrzej Siewior
2026-08-31 18:20 ` 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
2026-09-01 9:27 ` Alice Ryhl
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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