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b=SXTQAuyFjbWMPPMUqKkaSRAcMBq36NrPA0oqdoKXV3fmzIS0S5/925qLXowvn1G1N LmvyD0AgBJth3FQh5Pf3Jkus83C7+orgUi0zUXtZZ7OdQAt0O2fHIxicEJqoFHGtWE cIwrdVCDkCF1fTZoEpJAlCP+/BjQy5rjmgpQWtcbH2mnbIN5T4V+zff4nPCKgaqOnw daYuNsI0OnLuHFh74PqJ8HDn44rn4hFk3SwpiHiGOgfdlKs8TcEhA2VjxLi6doHSMb U9xBiGp0l48mhchI5b7QDw78Xq+VH9rv38U5BuWxJUOfwXmrvLpusVcTaE4K+iBM7I qYy/y6vfTU9Wg== Message-ID: Date: Mon, 24 Nov 2025 10:14:20 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/khugepaged: Fix skipping of alloc sleep after second failure To: Zhiheng Tao , akpm@linux-foundation.org, lorenzo.stoakes@oracle.com Cc: ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, shy828301@gmail.com, zokeefe@google.com, peterx@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <1763965157-58413-1-git-send-email-junchuan.tzh@antgroup.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: <1763965157-58413-1-git-send-email-junchuan.tzh@antgroup.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: B44BF1A0008 X-Stat-Signature: 7oijee65h4ndy6ajh9bx1if6gsneeo1o X-Rspam-User: X-HE-Tag: 1763975667-898198 X-HE-Meta: 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 qGgGrXHF nJQ+xcuT9SuL8AmV2jcHEI1hBNBSinsBGWMA0rjNw0bs5IUgJMLfOnTx6jQphtrP5M+xAIAnYBFrIt6SM+nZzJ0fZq+lW5AvIJSL3FJjhZLRHga0Bgmx9G0+vitCAvSBMhAx1tST3BQPyLaVbsga4d0tlSwUtZI63G1MvG3HQol6xSURrcKvjnQ2G/KkABcqzv2kXitn3NflS9lZ9XXjCJ8qshT+bbSTwShMDZ6ukOxUzhLlgl7CF1yLHL+wwDBW3abNH 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 11/24/25 07:19, Zhiheng Tao wrote: > In khugepaged_do_scan(), two consecutive allocation failures cause > the logic to skip the dedicated 60s throttling sleep > (khugepaged_alloc_sleep_millisecs), forcing a fallback to the > shorter 10s scanning interval via the outer loop > > Since fragmentation is unlikely to resolve in 10s, this results in > wasted CPU cycles on immediate retries. Why shouldn't memory comapction be able to compact a single THP in 10s? Why should it resolve in 60s? > > Reorder the failure logic to ensure khugepaged_alloc_sleep() is > always called on each allocation failure. > > Fixes: c6a7f445a272 ("mm: khugepaged: don't carry huge page to the next loop for !CONFIG_NUMA") What are we fixing here? This sounds like a change that might be better on some systems, but worse on others? We really need more information on when/how an issue was hit, and how this patch here really moves the needle in any way. -- Cheers David