From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id 80DA06B0038 for ; Mon, 25 Sep 2017 05:35:36 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id r83so12656385pfj.5 for ; Mon, 25 Sep 2017 02:35:36 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id f69si3673324pfj.623.2017.09.25.02.35.35 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 25 Sep 2017 02:35:35 -0700 (PDT) Date: Mon, 25 Sep 2017 11:35:32 +0200 From: Jan Kara Subject: Re: [PATCH 7/7] fs-writeback: only allow one inflight and pending full flush Message-ID: <20170925093532.GC5741@quack2.suse.cz> References: <1505921582-26709-1-git-send-email-axboe@kernel.dk> <1505921582-26709-8-git-send-email-axboe@kernel.dk> <20170921150510.GH8839@infradead.org> <728d4141-8d73-97fb-de08-90671c2897da@kernel.dk> <3682c4c2-6e8a-e883-9f62-455ea2944496@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3682c4c2-6e8a-e883-9f62-455ea2944496@kernel.dk> Sender: owner-linux-mm@kvack.org List-ID: To: Jens Axboe Cc: Christoph Hellwig , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, hannes@cmpxchg.org, clm@fb.com, jack@suse.cz On Thu 21-09-17 10:00:25, Jens Axboe wrote: > On 09/21/2017 09:36 AM, Jens Axboe wrote: > >> But more importantly once we are not guaranteed that we only have > >> a single global wb_writeback_work per bdi_writeback we should just > >> embedd that into struct bdi_writeback instead of dynamically > >> allocating it. > > > > We could do this as a followup. But right now the logic is that we > > can have on started (inflight), and still have one new queued. > > Something like the below would fit on top to do that. Gets rid of the > allocation and embeds the work item for global start-all in the > bdi_writeback structure. Hum, so when we consider stuff like embedded work item, I would somewhat prefer to handle this like we do for for_background and for_kupdate style writeback so that we don't have another special case. For these don't queue any item, we just queue writeback work into the workqueue (via wb_wakeup()). When flusher work gets processed wb_do_writeback() checks (after processing all normal writeback requests) whether conditions for these special writeback styles are met and if yes, it creates on-stack work item and processes it (see wb_check_old_data_flush() and wb_check_background_flush()). So in this case we would just set some flag in bdi_writeback when memory reclaim needs help and wb_do_writeback() would check for this flag and create and process writeback-all style writeback work. Granted this does not preserve ordering of requests (basically any specific request gets priority over writeback-whole-world request) but memory gets cleaned in either case so flusher should be doing what is needed. Honza -- Jan Kara SUSE Labs, CR -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org