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[90.233.217.11]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-55b88cabb8asm3154101e87.145.2025.08.08.09.56.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 Aug 2025 09:56:27 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Fri, 8 Aug 2025 18:56:25 +0200 To: Michal Hocko Cc: Uladzislau Rezki , linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , Baoquan He , LKML Subject: Re: [PATCH 8/8] mm: Drop __GFP_DIRECT_RECLAIM flag if PF_MEMALLOC is set Message-ID: References: <20250807075810.358714-1-urezki@gmail.com> <20250807075810.358714-9-urezki@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: jp1c939814s6h1ktnwdzmyziw9rngyde X-Rspam-User: X-Rspamd-Queue-Id: 9261620011 X-Rspamd-Server: rspam02 X-HE-Tag: 1754672190-435472 X-HE-Meta: U2FsdGVkX1+oa6tGnvn6Jmkmstt0Egz+ue5jwbTOM66dNpFe5XElJFiY3RBhSn+sH8J4EL/m8Zv/2ZgDZu0TJwGlmrt0uNpDPuMh5pTxjB/Zbz83wEaCDVu1q+QaIwXzTJk+NPFGe20w8unBvxUteyGVPtV2N45pgP27pfyeNG3WAB5pJKt1A2nkYhQibeUMKRuaASLFZrJEnc3B+mmCyRmk6VFAECWkvjTdsq2PAmpgXbLlsfwlntyqhxqX1sKvFT+ICjkOftQw1ALe6qF81PzTAuQNwr5sjqDAqT/7n279102sG1oy+x6LiMPYkfKosLWk/P6Mh7ENvfYx5REDikShFYbwooJaRvGvFL+KHZ/EJh7NtlRPrEddeeIvfHTxMS1yowYYkZARVn6WoPPU8lROzH9p3MX8z1OZ6ZShGUHjpePTAJVo2a6ooRnIl1T9HMhQmeI23eZd3ZZE8ovwNuDaCt94I8r20eQuyc3stDtHLcwjzFVPwUqJdvNzAtiCS8FURH2rzvVN8//87MzaWetBkAIXFZ3XWQdBfo0RdEifTNF/c9jiNoeWTu6skf461PGUhvJp6LGsuECBTmzIM0JqsFxvkl+dvbL2xQDId1rAqKKTbSrKYwQ/2Wy+U0dTeCpVkpLgdi7HTUG326BEmLQthLOGpC0Cw9g4lF2yT2JS0PCPd+UWbOru7RDMO7Rp8ciqfRfbZIRb/pEhNcISfrPIIwVgxYg35TiwdkgpWCKITzHBCeVqckel5qnB4AaVkVMHFugQxbpFzB1m8dTzPP9op3JYENb1XlNQ2GpzMgmlJOSE1YLYq12+t+1Kms96WudGi2F5JDW1tL5yMCzvbrPm8s/+XSkQVDbsBbS1ueQ9a89jWCvd4JvWtEmHtbfrG3RXpHWF9sDgMF82MqDPUm1X2okQ2M50e54TIev/pStJwh1pS9NYprd03/IZ0i7s+8L+H/6djgoX+NkSfbX OkPQCnmJ gJivZkqiu/JZjVmQNyQzxYzMq6C85xU7xo7aIPsNKzAcqguklF5IMzTYxTe9b3TIjHNC6+9FkYz7tpH84ap/zZQcTT4Q2ARsUS2ZlAb32/a6D/ZSOWgrx586p8GIO+zqg1okACZfrF+gGbbR3A6AipeVbEaNNFgsCFSg62Io1CL1EROjFSf++gEmeaFWEFIiXHus+LGkJesoU2HWEZX7ZXLkms1lYAtyXDlOShBYNipqu9ghETIWtDhmHsK1CDhTa6h1t2MzzfjKZ1qP2MgJFCZj4wViezn/4YWa4ro1xOgmXGgCcZlZoGP8FZYM9yxSRDRli5xOSJA7Z2ujv/HG/3KLY8tKg6NVTS8BAO1ZwwhQzBqDlvEnh2JvNK3IMwnfFYRrW4TUCdmn9WJe1Of4iSs5YNsNTV0Tr/yDND3L7vrie+HUWEyur0AjjtqDS2Z1WWtWgRW9t52V/hnTvbf8s3VUWClOb3Q1q2YZq 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, Aug 08, 2025 at 04:16:04PM +0200, Michal Hocko wrote: > On Fri 08-08-25 15:12:45, Uladzislau Rezki wrote: > > On Thu, Aug 07, 2025 at 01:58:20PM +0200, Michal Hocko wrote: > > > On Thu 07-08-25 09:58:10, Uladzislau Rezki wrote: > > > > The memory allocator already avoids reclaim when PF_MEMALLOC is set. > > > > Clear __GFP_DIRECT_RECLAIM explicitly to suppress might_alloc() warnings > > > > to make more correct behavior. > > > > > > Rather than chaning the gfp mask would it make more sense to update > > > might_alloc instead? > > > > > Hm.. I was thinking about it but decided to drop the __GFP_DIRECT_RECLAIM > > instead just to guarantee a no-reclaim behaviour, as it is written now to > > the flag. > > > > >From the other hand after this patch we would have some unneeded/dead > > checks(if i do not missing anything). For example: > > > > [1] > > WARN_ON_ONCE(!can_direct_reclaim); > > /* > > * PF_MEMALLOC request from this context is rather bizarre > > * because we cannot reclaim anything and only can loop waiting > > * for somebody to do a work for us. > > */ > > WARN_ON_ONCE(current->flags & PF_MEMALLOC); > > [2] > > /* no reclaim without waiting on it */ > > if (!(gfp_mask & __GFP_DIRECT_RECLAIM)) > > return false; > > > > /* this guy won't enter reclaim */ > > if (current->flags & PF_MEMALLOC) > > return false; > > > > [3] > > /* Caller is not willing to reclaim, we can't balance anything */ > > if (!can_direct_reclaim) > > goto nopage; > > > > /* Avoid recursion of direct reclaim */ > > if (current->flags & PF_MEMALLOC) > > goto nopage; > > etc. > > > > But, yes, might_alloc() can be modified also. > > I do not have a _strong_ preference but my slight preference would be to > deal with this in might_alloc. Not sure what other think. > No problem, that i can easily switch to. -- Uladzisau Rezki