From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B740FC7618F for ; Mon, 22 Jul 2019 22:26:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 87ED121985 for ; Mon, 22 Jul 2019 22:26:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563834370; bh=SaCZr/lqE3KBkwJxJ3lN9pVqMFlNvyqSapA1Iar2Yz4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=DyuqWeGi77JU8xnZHh8bwPJFXXcqEtK5Pan3rFV14lYlOwwA40AkqlIhWp5YIlsd7 mHlkF/pI97S87Q9OYfc2krgVbcKnCV8bLKgugRLLbQGsymXWOQKQBpONxuiTKXkMSS sG7TlJzbam1+r3YU3TZuYX7dCZSkvlEiiVGovdVM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732962AbfGVW0J (ORCPT ); Mon, 22 Jul 2019 18:26:09 -0400 Received: from mail.kernel.org ([198.145.29.99]:40010 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728633AbfGVW0J (ORCPT ); Mon, 22 Jul 2019 18:26:09 -0400 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 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org 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); _