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[109.228.58.192]) by mx.google.com with ESMTPS id z13si6233796wrq.58.2019.06.01.02.26.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 01 Jun 2019 02:26:44 -0700 (PDT) Received-SPF: neutral (google.com: 109.228.58.192 is neither permitted nor denied by best guess record for domain of chris@chris-wilson.co.uk) client-ip=109.228.58.192; Authentication-Results: mx.google.com; spf=neutral (google.com: 109.228.58.192 is neither permitted nor denied by best guess record for domain of chris@chris-wilson.co.uk) smtp.mailfrom=chris@chris-wilson.co.uk X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from localhost (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP (TLS) id 16757666-1500050 for multiple; Sat, 01 Jun 2019 10:26:25 +0100 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable To: Andrew Morton , Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org From: Chris Wilson In-Reply-To: <20190307153051.18815-1-willy@infradead.org> Cc: Matthew Wilcox , "Kirill A. Shutemov" , Hugh Dickins , Jan Kara , Song Liu References: <20190307153051.18815-1-willy@infradead.org> Message-ID: <155938118174.22493.11599751119608173366@skylake-alporthouse-com> User-Agent: alot/0.6 Subject: Re: [PATCH v4] page cache: Store only head pages in i_pages Date: Sat, 01 Jun 2019 10:26:21 +0100 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: Quoting Matthew Wilcox (2019-03-07 15:30:51) > Transparent Huge Pages are currently stored in i_pages as pointers to > consecutive subpages. This patch changes that to storing consecutive > pointers to the head page in preparation for storing huge pages more > efficiently in i_pages. > = > Large parts of this are "inspired" by Kirill's patch > https://lore.kernel.org/lkml/20170126115819.58875-2-kirill.shutemov@linux= .intel.com/ > = > Signed-off-by: Matthew Wilcox > Acked-by: Jan Kara > Reviewed-by: Kirill Shutemov > Reviewed-and-tested-by: Song Liu > Tested-by: William Kucharski > Reviewed-by: William Kucharski I've bisected some new softlockups under THP mempressure to this patch. They are all rcu stalls that look similar to: [ 242.645276] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: [ 242.645293] rcu: Tasks blocked on level-0 rcu_node (CPUs 0-3): P828 [ 242.645301] (detected by 1, t=3D5252 jiffies, g=3D55501, q=3D221) [ 242.645307] gem_syslatency R running task 0 828 815 0x0000= 4000 [ 242.645315] Call Trace: [ 242.645326] ? __schedule+0x1a0/0x440 [ 242.645332] ? preempt_schedule_irq+0x27/0x50 [ 242.645337] ? apic_timer_interrupt+0xa/0x20 [ 242.645342] ? xas_load+0x3c/0x80 [ 242.645347] ? xas_load+0x8/0x80 [ 242.645353] ? find_get_entry+0x4f/0x130 [ 242.645358] ? pagecache_get_page+0x2b/0x210 [ 242.645364] ? lookup_swap_cache+0x42/0x100 [ 242.645371] ? do_swap_page+0x6f/0x600 [ 242.645375] ? unmap_region+0xc2/0xe0 [ 242.645380] ? __handle_mm_fault+0x7a9/0xfa0 [ 242.645385] ? handle_mm_fault+0xc2/0x1c0 [ 242.645393] ? __do_page_fault+0x198/0x410 [ 242.645399] ? page_fault+0x5/0x20 [ 242.645404] ? page_fault+0x1b/0x20 Any suggestions as to what information you might want? -Chris