Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755041AbZAJXoo (ORCPT ); Sat, 10 Jan 2009 18:44:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750782AbZAJXoc (ORCPT ); Sat, 10 Jan 2009 18:44:32 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:58765 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750763AbZAJXob (ORCPT ); Sat, 10 Jan 2009 18:44:31 -0500 Date: Sun, 11 Jan 2009 00:43:52 +0100 From: Ingo Molnar To: Joerg Roedel Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, dwmw2@infradead.org, fujita.tomonori@lab.ntt.co.jp, netdev@vger.kernel.org, iommu@lists.linux-foundation.org Subject: Re: [PATCH 04/16] dma-debug: add allocator code Message-ID: <20090110234352.GA20843@elte.hu> References: <1231517970-20288-1-git-send-email-joerg.roedel@amd.com> <1231517970-20288-5-git-send-email-joerg.roedel@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1231517970-20288-5-git-send-email-joerg.roedel@amd.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1531 Lines: 50 * Joerg Roedel wrote: > + printk(KERN_ERR "DMA-API: debugging out of memory " > + "- disabling\n"); btw., i'd suggest to not break kernel messages mid-string, but do something like this instead: > + printk(KERN_ERR "DMA-API: debugging out of memory - disabling\n"); Also, i'd use WARN() - it might be useful to see what callsite depleted the pool. > + entry = list_entry(free_entries.next, struct dma_debug_entry, list); > + list_del(&entry->list); > + memset(entry, 0, sizeof(*entry)); > + > + num_free_entries -= 1; > + if (num_free_entries < min_free_entries) > + min_free_entries = num_free_entries; unlikely() i guess. Regarding the entry pool locking: > +static void dma_entry_free(struct dma_debug_entry *entry) > +{ > + unsigned long flags; > + > + /* > + * add to beginning of the list - this way the entries are > + * more likely cache hot when they are reallocated. > + */ > + spin_lock_irqsave(&free_entries_lock, flags); > + list_add(&entry->list, &free_entries); > + num_free_entries += 1; > + spin_unlock_irqrestore(&free_entries_lock, flags); it might make sense to cache entries in the buckets - hence reuse the bucket spinlock. This means a somewhat higher effective pool size, but it also avoids a global lock. Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/