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[109.81.94.157]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-427d2a635cdsm42509845e9.13.2024.07.19.01.01.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Jul 2024 01:01:10 -0700 (PDT) Date: Fri, 19 Jul 2024 10:01:09 +0200 From: Michal Hocko To: Barry Song <21cnbao@gmail.com> Cc: akpm@linux-foundation.org, linux-mm@kvack.org, Barry Song , Uladzislau Rezki , Christoph Hellwig , Lorenzo Stoakes , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com> Subject: Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 74DFE120012 X-Stat-Signature: 7ji9us6sx9g1hzfoxsoe8x7b9a8dnnq4 X-Rspam-User: X-HE-Tag: 1721376072-93385 X-HE-Meta: U2FsdGVkX19h/x6gEX7/YIgsdUnccFRUxjhJhQMX+vEoO3/ejFELHc7eKrJORm7MKrnqfj1DleRZ1ZemPRNx2Ao5KJMmWPitcBExWW3oHfGJgAvYDvlQASKxonqGgXCIJzYZaCtZfcmJlypHm6oO6sAUHAF3EI25x8hUirGetb9mUWmsChMr7j8eDtKGqilD2vptpzgR2wkIx/XrY1tLk5lwteUb7Ux7AJROtPmEQfLyeexGqTYyUbKYMVrGmcaqyPVwdeE41Kyjt7+mtzftiHPGagR8UyeOz3exYC3szo0IgXZnaQcdY0OXkuSF38/iy2FVWb++kP/RO5n96SahE8M0TdfCp2cQ0e1msg3QXm9fGMdNIE79gp0afRwYXqI5Pf4uo9sxgUKFD2viPyjeOMUgNna3YOiMrwoC0rMiOdoP1h68b1gASajTvyzod8Wm/Lt5fJFXcpctWkgpzD1WkwCEWIx1yk4ZaT55+pEW3RH/oTDGMzl30E5AEL3v2mzuIibBH61Jh7RgKAPX6LwwaGE/XuR6MdXZt1o255Iz40MewLHY7fdjYgeM9mddu7nrqEt6N06F3zX2VnX85xoowSJ2/KnltNGyT6ZYXyDAn/XIvU7ck3mgIDJtsFZxEw5XUBHTTBdh7Bb69PgjnLbZiyB4f22zSIMV7W4zznCiB8BgtUy/bYtqrcMlZfK14Wk9SAXzNySunJsgUxrvPVqv9cYxjT+YAn8eWqK1HLvAxx6QFWICcG9XlKKRIKpj3rTCWYIRP4a3FFxUyNyuFb/+6uB6+h9wXz66ImK/QLpy94eSYetL/pnX80HTKN3V8I6U6M0e/8l/E5alicJlYd19ePMfipygSQRyWhK2SHTx7JFnP7V3eOs20schlvP5GjGujEPop50rfwGbbtOzqFyku/zsexkmwTreoavkeoAMQNihvbjiCx7yB4KdX3EavksnhJydkEzhPSXDgS2vICc WNM9yAlq 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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 Fri 19-07-24 19:51:06, Barry Song wrote: > On Fri, Jul 19, 2024 at 7:42 PM Michal Hocko wrote: [...] > > It cannot reclaim itself and it cannot sleep to wait for the memory so > > NOFAIL semantic is simply impossible. We have put a warning in place to > > this is still "right" behaviour to retry infinitely at least according > to the doc of > __GFP_NOFAIL. I do not agree that implementing busy loop in the kernel is the right practice! > I assume getting new memory by many retries is still > possibly some other processes might be reclaiming or freeing memory > then providing free memory to this one being stuck. No, I strongly disagree we should even pretend this is a supported allocation strategy. NAK to any attempt to legalize it in some form. -- Michal Hocko SUSE Labs