From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f199.google.com (mail-io0-f199.google.com [209.85.223.199]) by kanga.kvack.org (Postfix) with ESMTP id 4AE3C6B0038 for ; Mon, 25 Sep 2017 10:48:49 -0400 (EDT) Received: by mail-io0-f199.google.com with SMTP id k101so13276777iod.1 for ; Mon, 25 Sep 2017 07:48:49 -0700 (PDT) Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id f192sor2732182iof.296.2017.09.25.07.48.47 for (Google Transport Security); Mon, 25 Sep 2017 07:48:48 -0700 (PDT) Subject: Re: [PATCH 7/7] fs-writeback: only allow one inflight and pending full flush 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> <20170925093532.GC5741@quack2.suse.cz> From: Jens Axboe Message-ID: Date: Mon, 25 Sep 2017 08:48:46 -0600 MIME-Version: 1.0 In-Reply-To: <20170925093532.GC5741@quack2.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Jan Kara Cc: Christoph Hellwig , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, hannes@cmpxchg.org, clm@fb.com On 09/25/2017 03:35 AM, Jan Kara wrote: > 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()). Thanks Jan, I think that's a really good suggestion and kills the special case completely. I'll rework the patch as a small series for 4.15. > 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. I don't think that matters, and we're already mostly there since we reject a request if one is pending. And at this point they are all identical "start all writeback" requests. -- Jens Axboe -- 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