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Wed, 25 Mar 2026 09:49:23 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Wed, 25 Mar 2026 17:49:22 +0100 To: "David Hildenbrand (Arm)" , Muhammad Usama Anjum Cc: Muhammad Usama Anjum , Uladzislau Rezki , Zi Yan , Andrew Morton , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Nick Terrell , David Sterba , Vishal Moola , linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, Ryan.Roberts@arm.com, david.hildenbrand@arm.com Subject: Re: [PATCH v3 2/3] vmalloc: Optimize vfree Message-ID: References: <20260324133538.497616-1-usama.anjum@arm.com> <20260324133538.497616-3-usama.anjum@arm.com> <1D88CFF0-8A74-413F-9A6A-39E27B760AE1@nvidia.com> <84f14a13-6236-47ef-afc5-e168d16caeec@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam12 X-Stat-Signature: u4d1ifguqb9u7nkguw69dcoa7zg6gdqm X-Rspamd-Queue-Id: 03C6840015 X-Rspam-User: X-HE-Tag: 1774457366-4217 X-HE-Meta: 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 GN9lXFsy 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Mar 25, 2026 at 05:34:08PM +0100, David Hildenbrand (Arm) wrote: > On 3/25/26 17:25, Muhammad Usama Anjum wrote: > > On 25/03/2026 4:16 pm, Uladzislau Rezki wrote: > >> On Wed, Mar 25, 2026 at 03:02:14PM +0000, Muhammad Usama Anjum wrote: > >>> Sorry, I didn't get it. How does having cond_resched() in this function > >>> affects __free_contig_range()? > >>> > >> It is not. What i am asking is about: > >> > >> > >> spin_lock(); > >> free_pages_bulk() > >> ... > >> > >> > >> so this is not allowed because there is cond_resched() call. We > >> can remove it and make it possible to invoke free_pages_bulk() under > >> spin-lock, __but__ only if for example other calls do not sleep: > >> > >> __free_contig_range() > >> memdesc_section() > >> free_prepared_contig_range() > >> ... > >> > >>> > >>> The current user of this function is only vfree() which is sleepable. > >>> > >> I know. But this function can be used by others soon or later. > >> > >> Another option is add a comment, saying that it is only for sleepable > >> contexts. > > Thank you for detailed response. I can move cond_resched() to vfree() and make > > free_pages_bulk() allowed to be called form sleepable context. But I feel the > > current implementation is better to avoid latency spikes. I'll put explicit > > comment that this function can only be called from sleepable contexts. > Sounds good! > That's probably good enough for now. It can accept arbitrarily large > areas, so the cond_resched() in there is the right thing to do. :) > I agree, since it will be available for other callers, adding the comment is a right way, so people know :) -- Uladzislau Rezki