From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f72.google.com (mail-oi0-f72.google.com [209.85.218.72]) by kanga.kvack.org (Postfix) with ESMTP id BB54B6B025F for ; Mon, 14 Aug 2017 12:17:14 -0400 (EDT) Received: by mail-oi0-f72.google.com with SMTP id f11so11570844oic.3 for ; Mon, 14 Aug 2017 09:17:14 -0700 (PDT) Received: from mail-it0-x22a.google.com (mail-it0-x22a.google.com. [2607:f8b0:4001:c0b::22a]) by mx.google.com with ESMTPS id m83si4827961oia.86.2017.08.14.09.17.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 14 Aug 2017 09:17:13 -0700 (PDT) Received: by mail-it0-x22a.google.com with SMTP id 76so20320222ith.0 for ; Mon, 14 Aug 2017 09:17:13 -0700 (PDT) Subject: Re: [PATCH v1 2/6] fs: use on-stack-bio if backing device has BDI_CAP_SYNC capability From: Jens Axboe References: <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> <51f7472a-977b-be69-2688-48f2a0fa6fb3@kernel.dk> <20170814150620.GA12657@bgram> <51893dc5-05a3-629a-3b88-ecd8e25165d0@kernel.dk> <20170814153059.GA13497@bgram> <0c83e7af-10a4-3462-bb4c-4254adcf6f7a@kernel.dk> Message-ID: <058b4ae5-c6e9-ff32-6440-fb1e1b85b6fd@kernel.dk> Date: Mon, 14 Aug 2017 10:17:09 -0600 MIME-Version: 1.0 In-Reply-To: <0c83e7af-10a4-3462-bb4c-4254adcf6f7a@kernel.dk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: 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 On 08/14/2017 09:38 AM, Jens Axboe wrote: > On 08/14/2017 09:31 AM, Minchan Kim wrote: >>> Secondly, generally you don't have slow devices and fast devices >>> intermingled when running workloads. That's the rare case. >> >> Not true. zRam is really popular swap for embedded devices where >> one of low cost product has a really poor slow nand compared to >> lz4/lzo [de]comression. > > I guess that's true for some cases. But as I said earlier, the recycling > really doesn't care about this at all. They can happily coexist, and not > step on each others toes. Dusted it off, result is here against -rc5: http://git.kernel.dk/cgit/linux-block/log/?h=cpu-alloc-cache I'd like to split the amount of units we cache and the amount of units we free, right now they are both CPU_ALLOC_CACHE_SIZE. This means that once we hit that count, we free all of the, and then store the one we were asked to free. That always keeps 1 local, but maybe it'd make more sense to cache just free CPU_ALLOC_CACHE_SIZE/2 (or something like that) so that we retain more than 1 per cpu in case and app preempts when sleeping for IO and the new task on that CPU then issues IO as well. Probably minor. Ran a quick test on nullb0 with 32 sync readers. The test was O_DIRECT on the block device, so I disabled the __blkdev_direct_IO_simple() bypass. With the above branch, we get ~18.0M IOPS, and without we get ~14M IOPS. Both ran with iostats disabled, to avoid any interference from that. -- 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