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[109.81.17.167]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-3b47285c903sm9457414f8f.90.2025.07.07.00.11.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Jul 2025 00:11:44 -0700 (PDT) Date: Mon, 7 Jul 2025 09:11:43 +0200 From: Michal Hocko To: "Uladzislau Rezki (Sony)" Cc: linux-mm@kvack.org, Andrew Morton , LKML , Baoquan He Subject: Re: [RFC 3/7] mm/vmalloc: Avoid cond_resched() when blocking is not permitted Message-ID: References: <20250704152537.55724-1-urezki@gmail.com> <20250704152537.55724-4-urezki@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250704152537.55724-4-urezki@gmail.com> X-Rspamd-Queue-Id: 6A56D140006 X-Stat-Signature: 5bksezmba64urqg9kmhmanwd4ypb9xgp X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1751872306-537900 X-HE-Meta: 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 LYAbK/qK +2wKNfVuJ3z1IHKjdaoxv9lGXX6qvWdIqHOWJyrNov3udtW3uNfRbTc52qfj/C9B5E69shIjkAFto+bni8sL0UvlS4yJY1xTeWXmY 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 04-07-25 17:25:33, Uladzislau Rezki wrote: > The vm_area_alloc_pages() function uses cond_resched() to yield the > CPU during potentially long-running loops. However, yielding should > only be done if the given GFP flags allow blocking. > > This patch avoids calling cond_resched() when the allocation context > is non-blocking(GFP_ATOMIC, GFP_NOWAIT). Do we even need those cond_resched calls? Both of them are called shortly after memory allocator which already yields CPU when allowed. > > Signed-off-by: Uladzislau Rezki (Sony) > --- > mm/vmalloc.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 8c375b8e269d..25d09f753239 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -3624,7 +3624,9 @@ vm_area_alloc_pages(gfp_t gfp, int nid, > pages + nr_allocated); > > nr_allocated += nr; > - cond_resched(); > + > + if (gfpflags_allow_blocking(gfp)) > + cond_resched(); > > /* > * If zero or pages were obtained partly, > @@ -3666,7 +3668,9 @@ vm_area_alloc_pages(gfp_t gfp, int nid, > for (i = 0; i < (1U << order); i++) > pages[nr_allocated + i] = page + i; > > - cond_resched(); > + if (gfpflags_allow_blocking(gfp)) > + cond_resched(); > + > nr_allocated += 1U << order; > } > > -- > 2.39.5 -- Michal Hocko SUSE Labs