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[198.145.29.99]) by mx.google.com with ESMTPS id e2si9636351pgf.256.2019.07.22.15.26.08 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 22 Jul 2019 15:26:08 -0700 (PDT) Received-SPF: pass (google.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=Ogi3k+rE; spf=pass (google.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 484D921985; Mon, 22 Jul 2019 22:26:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563834368; bh=SaCZr/lqE3KBkwJxJ3lN9pVqMFlNvyqSapA1Iar2Yz4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Ogi3k+rE6tk0IM0RMI1sxYzidV8NLfAQfkbaqZqpx47sIH3rytjrFbF0L2h9+viUc HXSYDvdHUkfN2kpbEa5fKWrQdie7drx8APmpPamwnuov0yvOqo0lk8hQ21R7nNODV1 D/z8/0j2BEGTqS2l1Mi4j87EjG/KCZECdTJfkpyY= Date: Mon, 22 Jul 2019 15:26:07 -0700 From: Andrew Morton To: Johannes Weiner Cc: linux-mm@kvack.org, linux-btrfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] psi: annotate refault stalls from IO submission Message-Id: <20190722152607.dd175a9d517a5f6af06a8bdc@linux-foundation.org> In-Reply-To: <20190722201337.19180-1-hannes@cmpxchg.org> References: <20190722201337.19180-1-hannes@cmpxchg.org> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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: On Mon, 22 Jul 2019 16:13:37 -0400 Johannes Weiner wrote: > psi tracks the time tasks wait for refaulting pages to become > uptodate, but it does not track the time spent submitting the IO. The > submission part can be significant if backing storage is contended or > when cgroup throttling (io.latency) is in effect - a lot of time is > spent in submit_bio(). In that case, we underreport memory pressure. It's a somewhat broad patch. How significant is this problem in the real world? Can we be confident that the end-user benefit is worth the code changes? > Annotate the submit_bio() paths (or the indirection through readpage) > for refaults and swapin to get proper psi coverage of delays there. > > Signed-off-by: Johannes Weiner > --- > fs/btrfs/extent_io.c | 14 ++++++++++++-- > fs/ext4/readpage.c | 9 +++++++++ > fs/f2fs/data.c | 8 ++++++++ > fs/mpage.c | 9 +++++++++ > mm/filemap.c | 20 ++++++++++++++++++++ > mm/page_io.c | 11 ++++++++--- > mm/readahead.c | 24 +++++++++++++++++++++++- We touch three filesystems. Why these three? Are all other filesystems OK or will they need work as well? > ... > > --- a/mm/filemap.c > +++ b/mm/filemap.c > > ... > > @@ -2753,11 +2763,14 @@ static struct page *do_read_cache_page(struct address_space *mapping, > void *data, > gfp_t gfp) > { > + bool refault = false; > struct page *page; > int err; > repeat: > page = find_get_page(mapping, index); > if (!page) { > + unsigned long pflags; > + That was a bit odd. This? --- a/mm/filemap.c~psi-annotate-refault-stalls-from-io-submission-fix +++ a/mm/filemap.c @@ -2815,12 +2815,12 @@ static struct page *do_read_cache_page(s void *data, gfp_t gfp) { - bool refault = false; struct page *page; int err; repeat: page = find_get_page(mapping, index); if (!page) { + bool refault = false; unsigned long pflags; page = __page_cache_alloc(gfp); _