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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> User-Agent: Evolution 3.44.2 (3.44.2-1.fc36) MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1655458749; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=pYVDkeTjcXwpFgTs741MZhZlNLoBRZaZ5V4UWlxIXOs=; b=fWaPsfTSLuk3rgOgHZRQbTcCazBW1JrBDtjN++FOPI7tGeISnQXyioHIpbEU/KlaXo4qDp QnUtCA4RDz+0Y8TVmXtRFFlHsY4qSgfZOfTCYbOi1e2l9DGKw3Rkyg/qVl15fMUpyHUjuI 01ZZ2LQWQH4FmQ1hOnB5nTsOc+BSTZg= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1655458749; a=rsa-sha256; cv=none; b=1yzbRKNgjCxobDrUgppz//1zfUyAd4NC2jc8lJ+gDlwGwCYmSGYOKAy+JkSlkxbfE6DQdf NyE9StjA1QunXfoFOSi9In1RsGwjkrUsrtWKQnGeoYDdLEPFTaiDaBhG4Yzf805MNFlV0j lOwHgfL4X3y3ySOe2VoiZuXoIgNbBg0= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=CCAUqAiK; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf25.hostedemail.com: domain of nsaenzju@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=nsaenzju@redhat.com Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=CCAUqAiK; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf25.hostedemail.com: domain of nsaenzju@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=nsaenzju@redhat.com X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 84601A009B X-Stat-Signature: 6dax41p96j3jyhukphtngpfrdthpmr3b X-HE-Tag: 1655458749-59508 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: 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) > =09=09migratetype =3D MIGRATE_MOVABLE; > =09} > =20 > -=09local_lock_irqsave(&pagesets.lock, flags); > -=09freed_pcp =3D free_unref_page_commit(page, migratetype, order, false)= ; > -=09local_unlock_irqrestore(&pagesets.lock, flags); > - > -=09if (unlikely(!freed_pcp)) > +=09zone =3D page_zone(page); > +=09pcp_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) \ ({ \ =09local_irq_save(flags); \ =091; }) > +=09pcp =3D pcpu_spin_trylock_irqsave(struct per_cpu_pages, lock, zone->p= er_cpu_pageset, flags); > +=09if (pcp) { > +=09=09free_unref_page_commit(pcp, zone, page, migratetype, order); > +=09=09pcp_spin_unlock_irqrestore(pcp, flags); > +=09} else { > =09=09free_one_page(page_zone(page), page, pfn, order, migratetype, FPI_= NONE); > +=09} > +=09pcp_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