From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ronald van Zantvoort Subject: obsolete option freelist_percent in documentation / question Date: Mon, 17 Aug 2015 11:01:31 +0200 Message-ID: <55D1A2EB.3030603@pcextreme.nl> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from support.pcextreme.nl ([109.72.87.231]:45547 "EHLO support.pcextreme.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751331AbbHQJHT (ORCPT ); Mon, 17 Aug 2015 05:07:19 -0400 Received: from ox.pcextreme.nl (ox01.pcextreme.nl [IPv6:2a00:f10:101::6f7b:25:143]) by support.pcextreme.nl (Postfix) with ESMTPS id 3129F2C2EF for ; Mon, 17 Aug 2015 11:01:32 +0200 (CEST) Received: from lianxiang.the-loeki.net (unknown [IPv6:2001:980:7936:0:6267:20ff:fea9:3b9c]) by ox.pcextreme.nl (Postfix) with ESMTPSA id EC85F540100 for ; Mon, 17 Aug 2015 11:01:31 +0200 (CEST) Sender: linux-bcache-owner@vger.kernel.org List-Id: linux-bcache@vger.kernel.org To: "linux-bcache@vger.kernel.org" Hi all, https://www.kernel.org/doc/Documentation/bcache.txt reports freelist_percent Size of the freelist as a percentage of nbuckets. Can be written to to increase the number of buckets kept on the freelist, which lets you artificially reduce the size of the cache at runtime. Mostly for testing purposes (i.e. testing how different size caches affect your hit rate), but since buckets are discarded when they move on to the freelist will also make the SSD's garbage collection easier by effectively giving it more reserved space. However, on dec. 17, 2013, the allocator reserves got reworked and this option disappeared. We're currently rolling out bcache on a number of older Intel SSD's which are notoriously bad on the GC part; they practically *need* a big chunk of reserved space to function properly. Of course we could go with a HPA or a smaller partition, but it'd be much more elegant to do this from within bcache itself; so is this still possible , now that this option obviously no longer exists, and if so, how? Thanks in advance! Ronald