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[109.81.31.43]) by smtp.gmail.com with UTF8SMTPSA id 4fb4d7f45d1cf-62f11390075sm5158227a12.40.2025.09.15.10.11.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Sep 2025 10:11:28 -0700 (PDT) Date: Mon, 15 Sep 2025 19:11:27 +0200 From: Michal Hocko To: "Uladzislau Rezki (Sony)" Cc: linux-mm@kvack.org, Andrew Morton , Baoquan He , LKML Subject: Re: [PATCH v2 04/10] mm/vmalloc: Avoid cond_resched() when blocking is not permitted Message-ID: References: <20250915134041.151462-1-urezki@gmail.com> <20250915134041.151462-5-urezki@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250915134041.151462-5-urezki@gmail.com> X-Stat-Signature: rgn3s98zgpxoxwdgpbjf8nzoeo67185k X-Rspam-User: X-Rspamd-Queue-Id: 1B2141C000F X-Rspamd-Server: rspam10 X-HE-Tag: 1757956289-266767 X-HE-Meta: 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 V24X+4vy u0xk6Y2zib/2Z9ZaoLb+qy5N1kpoBIWIuCkmCku+p6iUDkLBB0De8odM9W2aTrZ6PaXRobqguy6/v7Yv5aHfUViAfpVQDUBQGBrzsbBN5hIPl0KEOGEYX3OSjb59npgFSfMHLYdbwQGi2UwI48WiE0jVDj4iiwUGM6+xIbDeuWtvm4sUYmK84WiLdJBDe12oCfC7Qx88k2bMPgvKokZobmPZDdkdcEP+KdeONdL3nhx1ioP5eSMKJS368+2ndN2xTJkVK0LzQ0RgVXCxswl6KfvvtyjH1THqUD+41C0zyCZzI7H3rqvM2kwV+51p4yjScnrQijokrq9mxFy1eW2gApA9sJSPVQK4pLq3FoUJ4D5BLdgQw1MNtcefJRZdCELB/hirf 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 Mon 15-09-25 15:40:34, Uladzislau Rezki wrote: > vm_area_alloc_pages() contains the only voluntary reschedule points > along vmalloc() allocation path. They are needed to ensure forward > progress on PREEMPT_NONE kernels under contention for vmap metadata > (e.g. alloc_vmap_area()). > > However, yielding should only be done if the given GFP flags allow > blocking. This patch avoids calling cond_resched() when allocation > context is non-blocking(GFP_ATOMIC, GFP_NOWAIT). We do have cond_resched in the page allocator path, right? So unless I am missing something we can safely drope these. I thought we have discused this already. > 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 49a0f81930a8..b77e8be75f10 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -3633,7 +3633,9 @@ 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, > @@ -3675,7 +3677,9 @@ 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; > } > > -- > 2.47.3 -- Michal Hocko SUSE Labs