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[66.187.233.206]) by smtp.gmail.com with ESMTPSA id o10sm4629749qkg.83.2019.11.15.13.32.06 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 15 Nov 2019 13:32:07 -0800 (PST) Message-ID: <1573853525.5937.140.camel@lca.pw> Subject: Re: [PATCH] iommu/iova: silence warnings under memory pressure From: Qian Cai To: Joe Perches , jroedel@suse.de Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Date: Fri, 15 Nov 2019 16:32:05 -0500 In-Reply-To: References: <1573851046-32384-1-git-send-email-cai@lca.pw> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6 (3.22.6-10.el7) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2019-11-15 at 13:13 -0800, Joe Perches wrote: > On Fri, 2019-11-15 at 15:50 -0500, Qian Cai wrote: > > When running heavy memory pressure workloads, this 5+ old system is > > throwing endless warnings below because disk IO is too slow to recover > > from swapping. Since the volume from alloc_iova_fast() could be large, > > once it calls printk(), it will trigger disk IO (writing to the log > > files) and pending softirqs which could cause a loop and no progress > > from memory reclaim for days. > > [] > > diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c > > [] > > @@ -233,7 +233,7 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad, > > > > struct iova *alloc_iova_mem(void) > > { > > - return kmem_cache_alloc(iova_cache, GFP_ATOMIC); > > + return kmem_cache_alloc(iova_cache, GFP_ATOMIC | __GFP_NOWARN); > > } > > EXPORT_SYMBOL(alloc_iova_mem); > > Is notification ever useful? > > If so, maybe something like: > > struct iova *alloc_iova_mem(void) > { > void *mem = kmem_cache_alloc(iova_cache, GFP_ATOMIC | __GFP_NOWARN)_ > > WARN_RATELIMIT(!mem, "%s: unable to alloc cache\n", __func__); > > return mem; > } > > or maybe use printk_deferred or prink_deferred_once > > ? > Forgot to mentioned that errors are also reported in hpsa driver which is fine. hpsa 0000:03:00.0: DMAR: Allocating 1-page iova failed but warn_alloc() is way too expense for this old server.