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[109.81.80.221]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-3b79c3b9c7dsm26206779f8f.26.2025.08.07.04.22.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Aug 2025 04:22:37 -0700 (PDT) Date: Thu, 7 Aug 2025 13:22:36 +0200 From: Michal Hocko To: "Uladzislau Rezki (Sony)" Cc: 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: <20250807075810.358714-5-urezki@gmail.com> X-Stat-Signature: neknt7afrjuo7fbk47gos831tnuhbaag X-Rspam-User: X-Rspamd-Queue-Id: DE134120004 X-Rspamd-Server: rspam02 X-HE-Tag: 1754565758-573087 X-HE-Meta: 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 Ct5PITZv rDbnyzg0EzqQQScZ4imrSfH4B3p7CIDPUYAIDrQR322IM7ibPzatHx+RAH7pGmc0/Lyws4CBUeEn/A76uu7e8JBAA2P+Bfct2y4QswD0609DII+m8+3mriU9lFknTzrsUbiOhM6JQWIIrBlmrVTywDcQw73clROAahykKWkDiESZQc1ASsEPNJ3iXTeAf9qQrzXXo001bzWr5R8MgIeWt+az5uKXpKcHPVqgY/NvMtqVRN/nwYepFMdCQ4RRtsNLAKmAvXH5rShTTBt54kts/Ze9uzhPD1ZTJk/PeBXx7vuO3zc/Uz4U/E/BlhUxS1Q4x5GiHVH5slOP7YO8RRtvLKtnrQhWIXwlyKEufvJL7Hsv6VE7eXP+oqvdqL3haiuovf3yQtfZe9ktwRx0a9SwiRQRZ2w== 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 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! > --- > mm/vmalloc.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 81b6d3bde719..b0255e0c74b3 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -3633,7 +3633,6 @@ vm_area_alloc_pages(gfp_t gfp, int nid, > pages + nr_allocated); > > nr_allocated += nr; > - cond_resched(); > > /* > * If zero or pages were obtained partly, > @@ -3675,7 +3674,6 @@ vm_area_alloc_pages(gfp_t gfp, int nid, > for (i = 0; i < (1U << order); i++) > pages[nr_allocated + i] = page + i; > > - cond_resched(); > nr_allocated += 1U << order; > } > > -- > 2.39.5 > -- Michal Hocko SUSE Labs