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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <3d0f189b-faab-4452-b9cc-8f4e7a15025f@linux.alibaba.com> From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 960D7A0004 X-Stat-Signature: m6awk46xw5mxcqpfhx3c8rnzuk7e9mgz X-HE-Tag: 1770354781-995266 X-HE-Meta: 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 TbMbrkzL 3948haH8BZjx8pJk2S19CJfaFdxFUVjVFNYOgQXCNmgIA2qm8EADGuggrV3rFpdwkaiMaW5RXBHtnxYu5ap42odGhNvLrrWYl8Nx4F4muZVfk1gpoPtPgA+uSL5BBBGyQ3ofH0sCeWfhLj9xpyCiMr3bCVCFyo/0PMUawxKSZhI456Fv2EXf0QQBOtZw1ADK3DmZP1qpToFCgfKSl3uLyuHAZUK3qgNdIqey9YFeWechFDJ6wla9dCkD+/9k1W/xWEIMdwJ32VBrCSTEAJi3hlUYpgEU8Zn7dIGNuHu5X2cWXFUdUOFc/52aaVd5cpC0jo9NtEuEJ0e5uuw3GvKGb1mUaN9gVzB2kSQyFwAZPWJneQ5tfqpjTmpL/9A== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/6/26 12:31 PM, Sergey Senozhatsky wrote: > On (26/02/06 12:38), Sergey Senozhatsky wrote: > [..] >>>> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >>>> index eff9e3061925..fa6a018b20a8 100644 >>>> --- a/mm/khugepaged.c >>>> +++ b/mm/khugepaged.c >>>> @@ -1894,6 +1894,9 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, >>>> xas_set(&xas, index); >>>> folio = xas_load(&xas); >>>> + if (try_to_freeze()) >>>> + goto xa_unlocked; >>>> + >>>> VM_BUG_ON(index != xas.xa_index); >>>> if (is_shmem) { >>>> if (!folio) { >>> >>> Your analysis is reasonable. When the system is freezing, khugepaged is >>> still trying to swap-in shmem to collapse, which prevents the system from >>> entering suspend state. However, it’s not only shmem that will swap in, >>> collapsing anonymous folios may also trigger swap-in operations. >> >> Right, I thought about it but wasn't sure. Could the inner loop (e.g. >> collapse_file() in this particular case) loop long enough to fail suspend >> w/o ever giving the outer loop (khugepaged_do_scan()) a chance to freeze? Yes, that’s possible. However, if we add a try_to_freeze() check in the inner loop, we need to consider various scenarios (such as anonymous folio swap-in and other potential cases?), which feels too hacky to me. > For inner loops I wondered if cond_resched() could be an indicator of > where try_to_freeze() should be placed. Those cond_resched() calls > are there for a reason, after all. E.g. something like: > > --- > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index fa6a018b20a8..cee08466a069 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -2431,6 +2431,9 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result > unsigned long hstart, hend; > > cond_resched(); > + if (try_to_freeze()) > + break; > + > if (unlikely(hpage_collapse_test_exit_or_disable(mm))) { > progress++; > break; > @@ -2453,6 +2456,9 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result > bool mmap_locked = true; > > cond_resched(); > + if (try_to_freeze()) > + goto breakouterloop; > + > if (unlikely(hpage_collapse_test_exit_or_disable(mm))) > goto breakouterloop; This looks better than the previous version. Let’s also wait to see if others have any better suggestions.