From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yuanhan Liu Subject: Re: [PATCH 07/21] vhost: add iotlb helper functions Date: Fri, 8 Sep 2017 16:36:33 +0800 Message-ID: <20170908083633.GG9736@yliu-home> References: <20170831095023.21037-1-maxime.coquelin@redhat.com> <20170831095023.21037-8-maxime.coquelin@redhat.com> <20170908080855.GF9736@yliu-home> <8a9b486b-635a-ec70-76f9-de830ad21882@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: dev@dpdk.org, jfreiman@redhat.com, tiwei.bie@intel.com, mst@redhat.com, vkaplans@redhat.com, jasowang@redhat.com To: Maxime Coquelin Return-path: Received: from mail-pg0-f50.google.com (mail-pg0-f50.google.com [74.125.83.50]) by dpdk.org (Postfix) with ESMTP id D941E2E8B for ; Fri, 8 Sep 2017 10:36:41 +0200 (CEST) Received: by mail-pg0-f50.google.com with SMTP id 188so3861034pgb.2 for ; Fri, 08 Sep 2017 01:36:41 -0700 (PDT) Content-Disposition: inline In-Reply-To: <8a9b486b-635a-ec70-76f9-de830ad21882@redhat.com> List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Fri, Sep 08, 2017 at 10:24:58AM +0200, Maxime Coquelin wrote: > > > On 09/08/2017 10:08 AM, Yuanhan Liu wrote: > >On Thu, Aug 31, 2017 at 11:50:09AM +0200, Maxime Coquelin wrote: > >>diff --git a/lib/librte_vhost/iotlb.c b/lib/librte_vhost/iotlb.c > >>new file mode 100644 > >>index 000000000..1b739dae5 > >>--- /dev/null > >>+++ b/lib/librte_vhost/iotlb.c > >>@@ -0,0 +1,231 @@ > >>+/*- > >>+ * BSD LICENSE > >>+ * > >>+ * Copyright (c) 2017 Red Hat, Inc. > >>+ * Copyright (c) 2017 Maxime Coquelin > > > >I'm not a lawer, but I have been told many years before, that you don't > >have the copyright for the code you write for open source project, the > >company you work for does. > > > >Thus, it's more common to see something like following: > > Copyright , ... the commany ... > > Author: Some One <...@...> > > > >However, as you may have noticed, it's not common to put the authorship > >in the source files. Though I don't object it. > > I'm not a lawyer too. At least in other projects, it seems common the > author puts his name as copyright owner. > > I have no issue to change it to only keep Red Hat's one though. That's up to you. What I said before was JFYI :) > >[...] > >>+#define IOTLB_CACHE_SIZE 1024 > >>+ > >>+static void vhost_user_iotlb_cache_remove_all(struct vhost_virtqueue *vq) > > ^^^^^^^^^^^^ > >Note that it's not the DPDK coding style to define a function. > > Ok, I guess you mean: > static void > vhost_user_iotlb_cache_remove_all(struct vhost_virtqueue *vq) ? Yep. > >>+{ > >>+ struct vhost_iotlb_entry *node, *temp_node; > >>+ > >>+ rte_rwlock_write_lock(&vq->iotlb_lock); > >>+ > >>+ TAILQ_FOREACH_SAFE(node, &vq->iotlb_list, next, temp_node) { > >>+ TAILQ_REMOVE(&vq->iotlb_list, node, next); > >>+ rte_mempool_put(vq->iotlb_pool, node); > >>+ } > >>+ > >>+ rte_rwlock_write_unlock(&vq->iotlb_lock); > >>+} > >>+ > >>+void vhost_user_iotlb_cache_insert(struct vhost_virtqueue *vq, uint64_t iova, > >>+ uint64_t uaddr, uint64_t size, uint8_t perm) > >>+{ > >>+ struct vhost_iotlb_entry *node, *new_node; > >>+ int ret; > >>+ > >>+ ret = rte_mempool_get(vq->iotlb_pool, (void **)&new_node); > >>+ if (ret) { > >>+ RTE_LOG(ERR, VHOST_CONFIG, "IOTLB pool empty, invalidate cache\n"); > > > >It's a cache, why not considering remove one to get space for new one? > > It would mean having to track every lookups not to remove hot entries, > which would have an impact on performance. You were removing all caches, how can we do worse than that? Even a random evict would be better. Or, more simply, just to remove the head or the tail? --yliu > Moreover, the idea is to have the cache large enough, else you could > face packet drops due to random cache misses. > > We might consider to improve it, but I consider it an optimization that > could be implemented later if needed. > > >>+ vhost_user_iotlb_cache_remove_all(vq); > >>+ ret = rte_mempool_get(vq->iotlb_pool, (void **)&new_node); > >>+ if (ret) { > >>+ RTE_LOG(ERR, VHOST_CONFIG, "IOTLB pool still empty, failure\n"); > >>+ return; > >>+ } > >>+ }