From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH v1 2/6] fs: use on-stack-bio if backing device has BDI_CAP_SYNC capability References: <1502175024-28338-3-git-send-email-minchan@kernel.org> <20170808124959.GB31390@bombadil.infradead.org> <20170808132904.GC31390@bombadil.infradead.org> <20170809015113.GB32338@bbox> <20170809023122.GF31390@bombadil.infradead.org> <20170809024150.GA32471@bbox> <20170810030433.GG31390@bombadil.infradead.org> <20170811104615.GA14397@lst.de> <20c5b30a-b787-1f46-f997-7542a87033f8@kernel.dk> <20170814085042.GG26913@bbox> From: Jens Axboe Message-ID: <51f7472a-977b-be69-2688-48f2a0fa6fb3@kernel.dk> Date: Mon, 14 Aug 2017 08:36:00 -0600 MIME-Version: 1.0 In-Reply-To: <20170814085042.GG26913@bbox> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: Christoph Hellwig , Dan Williams , Matthew Wilcox , Andrew Morton , Linux Kernel Mailing List , linux-mm , Ross Zwisler , "karam . lee" , seungho1.park@lge.com, Dave Chinner , Jan Kara , Vishal Verma , "linux-nvdimm@lists.01.org" , kernel-team List-ID: On 08/14/2017 02:50 AM, Minchan Kim wrote: > Hi Jens, > > On Fri, Aug 11, 2017 at 08:26:59AM -0600, Jens Axboe wrote: >> On 08/11/2017 04:46 AM, Christoph Hellwig wrote: >>> On Wed, Aug 09, 2017 at 08:06:24PM -0700, Dan Williams wrote: >>>> I like it, but do you think we should switch to sbvec[] to >>>> preclude pathological cases where nr_pages is large? >>> >>> Yes, please. >>> >>> Then I'd like to see that the on-stack bio even matters for >>> mpage_readpage / mpage_writepage. Compared to all the buffer head >>> overhead the bio allocation should not actually matter in practice. >> >> I'm skeptical for that path, too. I also wonder how far we could go >> with just doing a per-cpu bio recycling facility, to reduce the cost >> of having to allocate a bio. The on-stack bio parts are fine for >> simple use case, where simple means that the patch just special >> cases the allocation, and doesn't have to change much else. >> >> I had a patch for bio recycling and batched freeing a year or two >> ago, I'll see if I can find and resurrect it. > > So, you want to go with per-cpu bio recycling approach to > remove rw_page? > > So, do you want me to hold this patchset? I don't want to hold this series up, but I do think the recycling is a cleaner approach since we don't need to special case anything. I hope I'll get some time to dust it off, retest, and post soon. -- 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