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[90.233.217.11]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-55b88c98ab8sm2960265e87.79.2025.08.08.03.08.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 Aug 2025 03:08:44 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Fri, 8 Aug 2025 12:08:42 +0200 To: Michal Hocko Cc: "Uladzislau Rezki (Sony)" , linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , Baoquan He , LKML Subject: Re: [PATCH 4/8] mm/vmalloc: Remove cond_resched() in vm_area_alloc_pages() Message-ID: References: <20250807075810.358714-1-urezki@gmail.com> <20250807075810.358714-5-urezki@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: jh34our3txqybyja8uj7di378eph1617 X-Rspamd-Queue-Id: 51935180010 X-Rspamd-Server: rspam10 X-Rspam-User: X-HE-Tag: 1754647728-389964 X-HE-Meta: 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 QHAApQfi 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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 Thu, Aug 07, 2025 at 01:22:36PM +0200, Michal Hocko wrote: > On Thu 07-08-25 09:58:06, Uladzislau Rezki wrote: > > The vm_area_alloc_pages() function uses cond_resched() to yield the > > CPU during potentially long-running loops. However, these loops are > > not considered long-running under normal conditions. > > To be more precise they can take long if they dive into the page > allocator but that already involves cond_rescheds where appropriate so > these are not needed in fact. > > > In non-blocking > > contexts, calling cond_resched() is inappropriate also. > > > > Remove these calls to ensure correctness for blocking/non-blocking > > contexts. This also simplifies the code path. In fact, a slow path > > of page allocator already includes reschedule points to mitigate > > latency. > > > > This patch was tested for !CONFIG_PREEMPT kernel and with large > > allocation chunks(~1GB), without triggering any "BUG: soft lockup" > > warnings. > > > > Signed-off-by: Uladzislau Rezki (Sony) > > Acked-by: Michal Hocko > > Thanks! > Updated the commit message. Right, it can take long time. Thank you! -- Uladzislau Rezki