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charset=us-ascii Content-Disposition: inline In-Reply-To: <20230412131302.cf42a7f4b710db8c18b7b676@linux-foundation.org> X-Rspamd-Queue-Id: CA50518000C X-Stat-Signature: 8p3txx11tbj7pm4rg96s7jqogogrtkpg X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1681330717-899968 X-HE-Meta: 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 qs7L+fnx fpUHODBtYUaw0G6JwWwrxFNzRtrU4sr0blahyRKzu+DWYXhurJj4yElPZ7cDuqcnCmBFgsrBbVhvNe8ySZIgjsNNKFAmnQX48bxRhpHv4iXiDbGGpRD+8TbPcBBYNqI7fClwF6PvAwOgoYpzs9XdPF++CbUZXDXvv3D74HiTPkdzzGbsYbHxYtBH9aWeOcD/ySk75tclINsQS9IJD6wWuCg4OCTt+JH4aAZ3gs8TNNymEexui4HZd/NUrQD9uX/PCoNOz+uZ6T+8qVDALgLN60zXMWXpPTgNSb67j0n92C8Bo1rYJIi/1T2VWivkL8wNFrQbsV3KEtjoI0ZU= 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: On Wed 12-04-23 13:13:02, Andrew Morton wrote: > Lots of questions (ie, missing information!) > > On Wed, 12 Apr 2023 19:59:39 +0000 Pasha Tatashin wrote: > > > HugeTLB pages have a struct page optimizations where struct pages for tail > > pages are freed. However, when HugeTLB pages are destroyed, the memory for > > struct pages (vmemmap) need to be allocated again. > > > > Currently, __GFP_NORETRY flag is used to allocate the memory for vmemmap, > > but given that this flag makes very little effort to actually reclaim > > memory the returning of huge pages back to the system can be problem. > > Are there any reports of this happening in the real world? > > > Lets > > use __GFP_RETRY_MAYFAIL instead. This flag is also performs graceful > > reclaim without causing ooms, but at least it may perform a few retries, > > and will fail only when there is genuinely little amount of unused memory > > in the system. > > If so, does this change help? > > If the allocation attempt fails, what are the consequences? > > What are the potential downsides to this change? Why did we choose > __GFP_NORETRY in the first place? > > What happens if we try harder (eg, GFP_KERNEL)? Mike was generous enough to make me remember https://lore.kernel.org/linux-mm/YCafit5ruRJ+SL8I@dhcp22.suse.cz/. GFP_KERNEL wouldn't make much difference becauset this is __GFP_THISNODE. But I do agree that the changelog should go into more details about why do we want to try harder now. I can imagine that shrinking hugetlb pool by a large amount of hugetlb pages might become a problem but is this really happening or is this a theoretical concern? -- Michal Hocko SUSE Labs