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[109.81.84.7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-483bd6854c7sm10875895e9.0.2026.02.24.06.34.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Feb 2026 06:34:20 -0800 (PST) Date: Tue, 24 Feb 2026 15:34:19 +0100 From: Michal Hocko To: Shakeel Butt Cc: Christoph Hellwig , Uladzislau Rezki , Mikulas Patocka , "Vishal Moola (Oracle)" , SeongJae Park , Andrew Morton , zkabelac@redhat.com, Matthew Sakai , linux-mm@kvack.org, dm-devel@lists.linux.dev Subject: Re: [PATCH] mm: allow __GFP_RETRY_MAYFAIL in vmalloc Message-ID: References: <32bd9bed-a939-69c4-696d-f7f9a5fe31d8@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: 88AC3A0009 X-Rspamd-Server: rspam02 X-Stat-Signature: pwxigbqebbmxyccmpnnbimhk96bkgjgw X-HE-Tag: 1771943663-376088 X-HE-Meta: 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 QEvZLb8M 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 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 Tue 24-02-26 06:22:15, Shakeel Butt wrote: > On Tue, Feb 24, 2026 at 06:03:13AM -0800, Christoph Hellwig wrote: > > On Tue, Feb 24, 2026 at 01:22:36PM +0100, Michal Hocko wrote: > > > One thing that we could do to improve __GFP_RETRY_MAYFAIL resp. > > > __GFP_NORETRY is to use NOWAIT allocation semantic for page table > > > allocations as those could be achieved by scoped allocation context. > > > This could cause pre-mature failure after the whole bunch of memory has > > > already been allocated for the backing pages but considering that page > > > table allocations should be more and more rare over system runtime it > > > might be just a reasonable workaround. WDYT? > > > > Why bother? __GFP_RETRY_MAYFAIL has pretty lose semantics. Trying > > too hard to allocate PTEs is not breaking the overall concept. > > > > One thing __GFP_RETRY_MAYFAIL is very clear about is to not trigger the > oom-killer which is not the case for GFP_KERNEL. There are users who explicitly > use __GFP_RETRY_MAYFAIL to avoid oom-killer. > > Mikulas, is that the reason you are using __GFP_RETRY_MAYFAIL in your use-case? yes https://lore.kernel.org/all/32bd9bed-a939-69c4-696d-f7f9a5fe31d8@redhat.com/T/#u -- Michal Hocko SUSE Labs