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([2a0c:5a80:1b12:b300:47b0:25ba:1a2e:72ac]) by smtp.gmail.com with ESMTPSA id n23-20020a05600c3b9700b0039c5224bfcbsm9337826wms.46.2022.06.17.02.39.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Jun 2022 02:39:05 -0700 (PDT) Message-ID: <04709b2d0dc702c9bf50f57cde125b07cdf54363.camel@redhat.com> Subject: Re: [PATCH 7/7] mm/page_alloc: Replace local_lock with normal spinlock From: Nicolas Saenz Julienne To: Mel Gorman , Andrew Morton Cc: Marcelo Tosatti , Vlastimil Babka , Michal Hocko , Hugh Dickins , LKML , Linux-MM Date: Fri, 17 Jun 2022 11:39:03 +0200 In-Reply-To: <20220613125622.18628-8-mgorman@techsingularity.net> References: <20220613125622.18628-1-mgorman@techsingularity.net> <20220613125622.18628-8-mgorman@techsingularity.net> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.44.2 (3.44.2-1.fc36) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mel, On Mon, 2022-06-13 at 13:56 +0100, Mel Gorman wrote: > @@ -3446,12 +3490,16 @@ void free_unref_page(struct page *page, unsigned = int order) > migratetype =3D MIGRATE_MOVABLE; > } > =20 > - local_lock_irqsave(&pagesets.lock, flags); > - freed_pcp =3D free_unref_page_commit(page, migratetype, order, false); > - local_unlock_irqrestore(&pagesets.lock, flags); > - > - if (unlikely(!freed_pcp)) > + zone =3D page_zone(page); > + pcp_trylock_prepare(UP_flags); Now that you're calling the *_irqsave() family of function you can drop pcp_trylock_prepare/finish() For the record in UP: #define spin_trylock_irqsave(lock, flags) \ ({ \ local_irq_save(flags); \ 1; }) > + pcp =3D pcpu_spin_trylock_irqsave(struct per_cpu_pages, lock, zone->per= _cpu_pageset, flags); > + if (pcp) { > + free_unref_page_commit(pcp, zone, page, migratetype, order); > + pcp_spin_unlock_irqrestore(pcp, flags); > + } else { > free_one_page(page_zone(page), page, pfn, order, migratetype, FPI_NONE= ); > + } > + pcp_trylock_finish(UP_flags); > } > =20 > /* As Vlastimil mentioned elsewhere, I also wonder if it makes sense to just bypass patch #5. Especially as its intent isn't true anymore: "As preparation for dealing with both of those problems, protect the lists with a spinlock. The IRQ-unsafe version of the lock is used because IRQs are already disabled by local_lock_irqsave. spin_trylock is used in preparation for a time when local_lock could be used instead of lock_lock_irqsave." --=20 Nicol=C3=A1s S=C3=A1enz