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Tue, 06 Nov 2018 02:42:26 +0000 Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserv0021.oracle.com (8.14.4/8.14.4) with ESMTP id wA62gOMJ030859 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 6 Nov 2018 02:42:24 GMT Received: from abhmp0020.oracle.com (abhmp0020.oracle.com [141.146.116.26]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id wA62gMqV004802; Tue, 6 Nov 2018 02:42:22 GMT Received: from ca-dmjordan1.us.oracle.com (/10.211.9.48) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 05 Nov 2018 18:42:21 -0800 Date: Mon, 5 Nov 2018 18:42:28 -0800 From: Daniel Jordan To: Alex Williamson Cc: Daniel Jordan , linux-mm@kvack.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, aarcange@redhat.com, aaron.lu@intel.com, akpm@linux-foundation.org, bsd@redhat.com, darrick.wong@oracle.com, dave.hansen@linux.intel.com, jgg@mellanox.com, jwadams@google.com, jiangshanlai@gmail.com, mhocko@kernel.org, mike.kravetz@oracle.com, Pavel.Tatashin@microsoft.com, prasad.singamsetty@oracle.com, rdunlap@infradead.org, steven.sistare@oracle.com, tim.c.chen@intel.com, tj@kernel.org, vbabka@suse.cz Subject: Re: [RFC PATCH v4 06/13] vfio: parallelize vfio_pin_map_dma Message-ID: <20181106024228.sxkn3s22mfkf7lcc@ca-dmjordan1.us.oracle.com> References: <20181105165558.11698-1-daniel.m.jordan@oracle.com> <20181105165558.11698-7-daniel.m.jordan@oracle.com> <20181105145141.6f9937f6@w520.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181105145141.6f9937f6@w520.home> User-Agent: NeoMutt/20180323-268-5a959c X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9068 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1811060020 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 05, 2018 at 02:51:41PM -0700, Alex Williamson wrote: > On Mon, 5 Nov 2018 11:55:51 -0500 > Daniel Jordan wrote: > > +static int vfio_pin_map_dma_chunk(unsigned long start_vaddr, > > + unsigned long end_vaddr, > > + struct vfio_pin_args *args) > > { > > - dma_addr_t iova = dma->iova; > > - unsigned long vaddr = dma->vaddr; > > - size_t size = map_size; > > + struct vfio_dma *dma = args->dma; > > + dma_addr_t iova = dma->iova + (start_vaddr - dma->vaddr); > > + unsigned long unmapped_size = end_vaddr - start_vaddr; > > + unsigned long pfn, mapped_size = 0; > > long npage; > > - unsigned long pfn, limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT; > > int ret = 0; > > > > - while (size) { > > + while (unmapped_size) { > > /* Pin a contiguous chunk of memory */ > > - npage = vfio_pin_pages_remote(dma, vaddr + dma->size, > > - size >> PAGE_SHIFT, &pfn, limit); > > + npage = vfio_pin_pages_remote(dma, start_vaddr + mapped_size, > > + unmapped_size >> PAGE_SHIFT, > > + &pfn, args->limit, args->mm); > > if (npage <= 0) { > > WARN_ON(!npage); > > ret = (int)npage; > > @@ -1052,22 +1067,50 @@ static int vfio_pin_map_dma(struct vfio_iommu *iommu, struct vfio_dma *dma, > > } > > > > /* Map it! */ > > - ret = vfio_iommu_map(iommu, iova + dma->size, pfn, npage, > > - dma->prot); > > + ret = vfio_iommu_map(args->iommu, iova + mapped_size, pfn, > > + npage, dma->prot); > > if (ret) { > > - vfio_unpin_pages_remote(dma, iova + dma->size, pfn, > > + vfio_unpin_pages_remote(dma, iova + mapped_size, pfn, > > npage, true); > > break; > > } > > > > - size -= npage << PAGE_SHIFT; > > - dma->size += npage << PAGE_SHIFT; > > + unmapped_size -= npage << PAGE_SHIFT; > > + mapped_size += npage << PAGE_SHIFT; > > } > > > > + return (ret == 0) ? KTASK_RETURN_SUCCESS : ret; > > Overall I'm a big fan of this, but I think there's an undo problem > here. Per 03/13, kc_undo_func is only called for successfully > completed chunks and each kc_thread_func should handle cleanup of any > intermediate work before failure. That's not done here afaict. Should > we be calling the vfio_pin_map_dma_undo() manually on the completed > range before returning error? Yes, we should be, thanks very much for catching this. At least I documented what I didn't do? :) > > > +} > > + > > +static void vfio_pin_map_dma_undo(unsigned long start_vaddr, > > + unsigned long end_vaddr, > > + struct vfio_pin_args *args) > > +{ > > + struct vfio_dma *dma = args->dma; > > + dma_addr_t iova = dma->iova + (start_vaddr - dma->vaddr); > > + dma_addr_t end = dma->iova + (end_vaddr - dma->vaddr); > > + > > + vfio_unmap_unpin(args->iommu, args->dma, iova, end, true); > > +} > > + > > +static int vfio_pin_map_dma(struct vfio_iommu *iommu, struct vfio_dma *dma, > > + size_t map_size) > > +{ > > + unsigned long limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT; > > + int ret = 0; > > + struct vfio_pin_args args = { iommu, dma, limit, current->mm }; > > + /* Stay on PMD boundary in case THP is being used. */ > > + DEFINE_KTASK_CTL(ctl, vfio_pin_map_dma_chunk, &args, PMD_SIZE); > > PMD_SIZE chunks almost seems too convenient, I wonder a) is that really > enough work per thread, and b) is this really successfully influencing > THP? Thanks, Yes, you're right on both counts. I'd been using PUD_SIZE for a while in testing and meant to switch it back to KTASK_MEM_CHUNK (128M) but used PMD_SIZE by mistake. PUD_SIZE chunks have made thread finishing times too spread out in some cases, so 128M seems to be a reasonable compromise. Thanks for the thorough and quick review. Daniel