From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752294Ab1GLJgt (ORCPT ); Tue, 12 Jul 2011 05:36:49 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:42751 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750808Ab1GLJgs (ORCPT ); Tue, 12 Jul 2011 05:36:48 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Message-ID: <4E1C15B2.9020800@jp.fujitsu.com> Date: Tue, 12 Jul 2011 18:36:50 +0900 From: KOSAKI Motohiro User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; ja; rv:1.9.2.18) Gecko/20110616 Lightning/1.0b2 Thunderbird/3.1.11 MIME-Version: 1.0 To: chris@chris-wilson.co.uk CC: keithp@keithp.com, linux-kernel@vger.kernel.org, airlied@linux.ie, dri-devel@lists.freedesktop.org Subject: Re: [PATCH] i915: slab shrinker have to return -1 if it cant shrink any objects References: <4E0444CA.3080407@jp.fujitsu.com> <1309424153_44559@CP5-2952> In-Reply-To: <1309424153_44559@CP5-2952> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, sorry for the delay. > On Wed, 29 Jun 2011 20:53:54 -0700, Keith Packard wrote: >> On Fri, 24 Jun 2011 17:03:22 +0900, KOSAKI Motohiro wrote: >> >>> Now, i915_gem_inactive_shrink() should return -1 instead of 0 if it >>> can't take a lock. Otherwise, vmscan is getting a lot of confusing >>> because vmscan can't distinguish "can't take a lock temporary" and >>> "we've shrank all of i915 objects". >> >> This doesn't look like the cleanest change possible. I think it would be >> better if the shrink function could uniformly return an error >> indication so that we wouldn't need the weird looking conditional return. shrink_icache_memory() is good sample code. It doesn't take a lock if sc->nr_to_scan==0. i915_gem_inactive_shrink() should do it too, ideally. My patch only take a first-aid. Plus, if I understand correctly, i915_gem_inactive_shrink() have more fundamental issue. actually, shrinker code shouldn't use mutex. Instead, use spinlock. IOW, Don't call kmalloc(GFP_KERNEL) while taking dev->struct_mutex. Otherwise, vmscan in its call path completely fail to shrink i915 cache and it makes big memory reclaim confusing if i915 have a lot of shrinkable pages. > Unless I am mistaken, and there are more patches in flight, the return > code from i915_gem_inactive_shrink() is promoted to unsigned long and then > used in the calculation of how may objects to evict... shrinker->shrink has int type value. you can't change i915_gem_inactive_shrink() unless generic shrinker code. Do you really want to change it?