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Wed, 30 Oct 2024 17:42:53 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id CZUiMR1wImceSAAAD6G6ig (envelope-from ); Wed, 30 Oct 2024 17:42:53 +0000 Message-ID: <87aedec7-3890-4a35-9f72-b4edb8e1c390@suse.cz> Date: Wed, 30 Oct 2024 18:42:53 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/gup: restore the ability to pin more than 2GB at a time Content-Language: en-US To: John Hubbard , Christoph Hellwig Cc: Andrew Morton , LKML , linux-mm@kvack.org, linux-stable@vger.kernel.org, Vivek Kasireddy , David Hildenbrand , Dave Airlie , Gerd Hoffmann , Matthew Wilcox , Jason Gunthorpe , Peter Xu , Arnd Bergmann , Daniel Vetter , Dongwon Kim , Hugh Dickins , Junxiao Chang , Mike Kravetz , Oscar Salvador References: <20241030030116.670307-1-jhubbard@nvidia.com> <249d2614-0bcc-4ca8-b24e-7c0578a81dce@nvidia.com> <87124c1d-5b95-4499-aa4b-22f2ecd376bc@suse.cz> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: BAA48100011 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: bm7kyf56h31kbxue68xw9635fi9b7wy7 X-HE-Tag: 1730310146-265947 X-HE-Meta: U2FsdGVkX19uYZiWxqYDqxcUu4wIGUAXwaqjcMth9NY96+uqZ98rtwcaBQkXoY1vJP8Hxi26zMSnf95WwLpI1PRThJ7xZXI/gOrcJVDsoc9uEkzXIQvWRyhpy0GNDYI5FKQxyDUqJcrdiMYwT1uf0cyJuxWRWkkYJ09NdN2Bzto1Ytr9CUZpIXLn61FliIixC4J7kWoqAfDVcJV8yY3FXnpwAIXh241cryXUzqGVY3fhmxmIy9+ryQikSC6EKE0BBn27CFWPYT5dGdZDd6SuXz99eTxJ3lWvGdkDh3ad7jSdfDpGQhLpiqEiQR0TjKly5R9ZCUrlnBfd3ddVKeTkNvaQ0CKi/c6UTb0URplWznzFUj3WNcScCcgPId2ZGgIhkJO+EHiljeuzKMGajdOVWvXjtkUGzV8ZPt5A5BtU+3Ncq5eciq3FNdsm8AQ86B0uQtFOdb/n1D3ujFT6SJaaUGE9XlYIy0uvSGUX5FVPSglM5p1ESV/USfH05ZcAppSwH9v1s2oHyVLaSxrpuah2HPtB/qRtwLJySar/xMa6twZcBCvhBhJvfre/qQZnkxzJDYnp+FZxas40eC7EKgi8NwJjXjzKjWoVsjvhO7lywfdZZpzf8ZgVyWY7FvhK6k4U6MXE6AETOXKQjZO7DSmcjReSuJ/cL+ARusNmuMMVx4SwuWDAIpKkaDwEHVylM54v5F8psGooDildNX6Q4g1pbDj65GFYUu6PGzcw3jvrTKJkSXS7cwvdWG9gvLv+48kPtx/uHZ0lPAQiiE9MGBdiqkqnOgj2TcS+nBTWULNDJZHE+iFbjGLDo8/c7Jj2HDg7ukYxwg0o10DmBZFEG7fhncK3/yPS2UYRXscjrtmvtYz1UuI7PzbP4jXpilS6vMnxceuh3YW6uXS/Dq8tz94bohZuKfodVhXRPNFXOQjlkxI35uetXB4laDXwsO9wAeCbPUSDSJD1XiHs8wlllTa Q1gJpvyB XGN1VqWRqnHGZg/pv3ZHpeeJSfFnJbqDoo/yt8++gwd0kGGB11fOfqBa05LcVS3cUyiIpoqsF4FPeOGUfGmGNTGIeUj00JSDE+wtWsnDXSHrugEReNAJlHKt2pU7G69eTEgf2J1Ni5/o7S/7vbG7gTOMoT/73RSm58C+bFJ7FHAMPeAULZS+IxOL5ZHFTCtymmpOUyM3eBKeLd38+G6FB5jI+IUzdstz2Jmn79/CgQZAPdppOZ5MqCbKMPVA7i986j2fF4LQ0x7WGp4gUN+9ZMxfkx4NYdYFUvPFBxwQK5nqn+uASAnnNjEA/G0fZT0YSdb3c 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 10/30/24 18:29, John Hubbard wrote: > On 10/30/24 4:03 AM, Vlastimil Babka wrote: >> On 10/30/24 05:39, John Hubbard wrote: >>> On 10/29/24 9:33 PM, Christoph Hellwig wrote: >>>> On Tue, Oct 29, 2024 at 09:30:41PM -0700, John Hubbard wrote: > ... >> It might be a regression even if you don't try to pin over 2GB. high-order >> (>costly order) allocations can fail and/or cause disruptive >> reclaim/compaction cycles even below MAX_PAGE_ORDER and it's better to use >> kvmalloc if physical contiguity is not needed, it will attempt the physical >> kmalloc() allocation with __GFP_NORETRY (little disruption) and fallback to >> vmalloc() quickly. >> >> Of course if there's a way to avoid the allocation completely, even beter. > > Why not both? I'm going to ask our driver team to batch the pinning calls, > as recommended nearby, just to be sure that we are following best > practices. > > But it also seems good to use kvmalloc() here, and avoid any other > regressions. That's also a best practice. By "avoid the allocation completely" I meant David's proof of concept elsewhere in this thread, that seems to replace that kmalloc_array() with no allocation :) > thanks,