From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 6C42223D2B1 for ; Mon, 12 Oct 2026 11:03:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791802985; cv=none; b=CE3T1HrcMDYTi4V3sMIBS2Zx50a/8CHYFae3FGvtCHPTohQjm7DI0BJUtnb7KWVEcUEt6ijk9STNezoMyFr6PZWfSg9Qd9aa9AixWLOsaMIki40CC5I635cfM2aF6NOZiTDBCBijHSdOXlmvuEZ3S2yP06hwLJwtdvyHz4ehdx4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791802985; c=relaxed/simple; bh=t7K7/byZ5+qEcW0iCjnfxtEw/Jf2IhttUJ/wL+Jq1EQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=TI50Nh3h2mqEPo0jp+4bfihnSYQY4gVjffrnVeSzUNNMC/gTW58RpFXozN4wTt9FN4SSjM0+teQui6M2GYdkf1broPKJjOE+wfvc4Z/8dxeFK5tMrtJuATJxcPJW/8SZ3JcQUAU7YjPDDy0eE/vQmeO/uEh3FkAgh38wYrrvT6g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=L21goNgx; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="L21goNgx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 962781F0089B; Mon, 12 Oct 2026 11:03:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791802984; bh=zOT/mXYnt79hUkUdKkSBP3XTVF0egYdf5lOG5CmCa3s=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=L21goNgxr/CsmljAiIMApowzvwewI1oHLWrAq+U1ix5Ssl+Z6YbY/801flfTVaHxP R9Bhvat4zbeQHpcuMYCpIK5nmiB5+rv62vh1Q8TX6wMRUKCdvx1nzkP5AJjJx0rjT6 8I6MohVL0GvdTEQhk5xaaBljfYMhRx/W5DDp/8NPODtXcfApC2CjCzvT7mxtZxGQGG 7WHiTcpArTJitz4TAQu5kXTLfFTV1M0XYDtwtD7RziEWy9TOTe5iT17Hj9TJ4u3eq1 cgphmsDTcs9QJLFWAFy22MY8+PT2rW5/GIoHCBBPhCMcG0nz85gtNnleCOaoGCIHJS LKh/T7eE0Ciiw== Message-ID: Date: Mon, 12 Oct 2026 13:02:59 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/madvise: add cond_resched() in THP branch of madvise_cold_or_pageout_pte_range() To: albin_yang@163.com, akpm@linux-foundation.org, liam@infradead.org, ljs@kernel.org Cc: vbabka@kernel.org, jannh@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, albinwyang@tencent.com References: <20261010024042.4070048-1-albin_yang@163.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/10/26 04:40, albin_yang@163.com wrote: > From: Wei Yang > > During stress testing with stress-ng on a 256-CPU system, a softlockup > was observed when madvise(MADV_COLD) was called on a 31GB memory region > backed by transparent hugepages. The region contains 15935 THP PMD > entries, and the softlockup was triggered after 14485 of them had been > processed. > > The THP branch of madvise_cold_or_pageout_pte_range() has no scheduling > point. walk_pmd_range() invokes it once per 2MB PMD entry with no > cond_resched() anywhere in the loop. Each iteration calls > pmdp_invalidate() which issues a synchronous TLB shootdown (dsb ish) > waiting for all CPUs to acknowledge. This operation can be > time-consuming under heavy system load, causing the accumulated time > across all PMD entries to exceed the softlockup threshold (20s) and > panic when softlockup_panic=1. On a CONFIG_PREEMPT_NONE=y kernel, there > is no other opportunity to reschedule during this entire traversal. > > The regular PTE path already has an unconditional cond_resched() at the > function tail (introduced by commit 9c276cc65a58 ("mm: introduce > MADV_COLD") and commit 1a4e58cce84e ("mm: introduce MADV_PAGEOUT") when > MADV_COLD and MADV_PAGEOUT were first introduced) and a conditional one > inside the loop (commit b2f557a21bc8 ("mm/madvise: add cond_resched() > in madvise_cold_or_pageout_pte_range()")). The THP branch never > received equivalent treatment. That's quite a text to say "Do it just like the PTE case" ;) Acked-by: David Hildenbrand (Arm) -- Cheers, David