From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 21692C282CE for ; Tue, 4 Jun 2019 06:56:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0142D24DFC for ; Tue, 4 Jun 2019 06:56:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726697AbfFDG4O (ORCPT ); Tue, 4 Jun 2019 02:56:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57124 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726547AbfFDG4N (ORCPT ); Tue, 4 Jun 2019 02:56:13 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 49F773078AB6; Tue, 4 Jun 2019 06:56:13 +0000 (UTC) Received: from ming.t460p (ovpn-8-18.pek2.redhat.com [10.72.8.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7AB3110013D9; Tue, 4 Jun 2019 06:56:03 +0000 (UTC) Date: Tue, 4 Jun 2019 14:55:59 +0800 From: Ming Lei To: Guenter Roeck Cc: James Bottomley , linux-scsi@vger.kernel.org, "Martin K . Petersen" , linux-block@vger.kernel.org, Christoph Hellwig , Bart Van Assche , "Ewan D . Milne" , Hannes Reinecke Subject: Re: [PATCH V4 3/3] scsi: core: avoid to pre-allocate big chunk for sg list Message-ID: <20190604065558.GA6059@ming.t460p> References: <20190428073932.9898-1-ming.lei@redhat.com> <20190428073932.9898-4-ming.lei@redhat.com> <20190603204422.GA7240@roeck-us.net> <20190604010002.GA24432@ming.t460p> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.48]); Tue, 04 Jun 2019 06:56:13 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Mon, Jun 03, 2019 at 08:49:10PM -0700, Guenter Roeck wrote: > On 6/3/19 6:00 PM, Ming Lei wrote: > > On Mon, Jun 03, 2019 at 01:44:22PM -0700, Guenter Roeck wrote: > > > On Sun, Apr 28, 2019 at 03:39:32PM +0800, Ming Lei wrote: > > > > Now scsi_mq_setup_tags() pre-allocates a big buffer for IO sg list, > > > > and the buffer size is scsi_mq_sgl_size() which depends on smaller > > > > value between shost->sg_tablesize and SG_CHUNK_SIZE. > > > > > > > > Modern HBA's DMA is often capable of deadling with very big segment > > > > number, so scsi_mq_sgl_size() is often big. Suppose the max sg number > > > > of SG_CHUNK_SIZE is taken, scsi_mq_sgl_size() will be 4KB. > > > > > > > > Then if one HBA has lots of queues, and each hw queue's depth is > > > > high, pre-allocation for sg list can consume huge memory. > > > > For example of lpfc, nr_hw_queues can be 70, each queue's depth > > > > can be 3781, so the pre-allocation for data sg list is 70*3781*2k > > > > =517MB for single HBA. > > > > > > > > There is Red Hat internal report that scsi_debug based tests can't > > > > be run any more since legacy io path is killed because too big > > > > pre-allocation. > > > > > > > > So switch to runtime allocation for sg list, meantime pre-allocate 2 > > > > inline sg entries. This way has been applied to NVMe PCI for a while, > > > > so it should be fine for SCSI too. Also runtime sg entries allocation > > > > has verified and run always in the original legacy io path. > > > > > > > > Not see performance effect in my big BS test on scsi_debug. > > > > > > > > > > This patch causes a variety of boot failures in -next. Typical failure > > > pattern is scsi hangs or failure to find a root file system. For example, > > > on alpha, trying to boot from usb: > > > > I guess it is because alpha doesn't support sg chaining, and > > CONFIG_ARCH_NO_SG_CHAIN is enabled. ARCHs not supporting sg chaining > > can only be arm, alpha and parisc. > > > > I don't think it is that simple. I do see the problem on x86 (32 and 64 bit) > sparc, ppc, and m68k as well, and possibly others (I didn't check all because > -next is in terrible shape right now). Error log is always a bit different > but similar. > > On sparc: > > scsi host0: Data transfer overflow. > scsi host0: cur_residue[0] tot_residue[-181604017] len[8192] > scsi host0: DMA length is zero! > scsi host0: cur adr[f000f000] len[00000000] > scsi host0: Data transfer overflow. > scsi host0: cur_residue[0] tot_residue[-181604017] len[8192] > scsi host0: DMA length is zero! > > On ppc: > > scsi host0: DMA length is zero! > scsi host0: cur adr[0fd21000] len[00000000] > scsi host0: Aborting command [(ptrval):28] > scsi host0: Current command [(ptrval):28] > scsi host0: Active command [(ptrval):28] > > On x86, x86_64 (after reverting a different crash-causing patch): > > [ 20.226809] scsi host0: DMA length is zero! > [ 20.227459] scsi host0: cur adr[00000000] len[00000000] > [ 50.588814] scsi host0: Aborting command [(____ptrval____):28] > [ 50.589210] scsi host0: Current command [(____ptrval____):28] > [ 50.589447] scsi host0: Active command [(____ptrval____):28] > [ 50.589674] scsi host0: Dumping command log > > On m68k there is a crash. > > Unable to handle kernel NULL pointer dereference at virtual address (ptrval) > Oops: 00000000 > Modules linked in: > PC: [<00203a9e>] esp_maybe_execute_command+0x31e/0x46c > SR: 2704 SP: (ptrval) a2: 07c1ea20 > d0: 00000002 d1: 00000400 d2: 00000000 d3: 00002000 > d4: 00000000 d5: 00000000 a0: 07db753c a1: 00000000 > Process kworker/0:0H (pid: 4, task=(ptrval)) > Frame format=7 eff addr=00000020 ssw=0505 faddr=00000020 > wb 1 stat/addr/data: 0000 00000000 00000000 > wb 2 stat/addr/data: 0000 00000000 00000000 > wb 3 stat/addr/data: 0000 00000020 00000000 > push data: 00000000 00000000 00000000 00000000 > Stack from 07c2be08: > ... > Call Trace: [<00002000>] _start+0x0/0x8 > [<001f65ca>] scsi_mq_done+0x0/0x2c > [<001887fe>] blk_mq_get_driver_tag+0x0/0xba > [<00188800>] blk_mq_get_driver_tag+0x2/0xba > [<00025aec>] create_worker+0x0/0x14e > [<00203f64>] esp_queuecommand+0x9c/0xa2 > [<00203f3a>] esp_queuecommand+0x72/0xa2 > [<001f7fd4>] scsi_queue_rq+0x54e/0x5ba > [<00188b4a>] blk_mq_dispatch_rq_list+0x292/0x38a > [<00188656>] blk_mq_dequeue_from_ctx+0x0/0x1a8 > [<001888b8>] blk_mq_dispatch_rq_list+0x0/0x38a > [<00025aec>] create_worker+0x0/0x14e > ... > > All those problems are fixed by reverting this patch. All above problem is esp_scsi specific, and esp_scsi does not support sg chain. I will try to figure out one patch to cover all. esp_map_dma(): if (esp->flags & ESP_FLAG_NO_DMA_MAP) { /* * For pseudo DMA and PIO we need the virtual address instead of * a dma address, so perform an identity mapping. */ spriv->num_sg = scsi_sg_count(cmd); for (i = 0; i < spriv->num_sg; i++) { sg[i].dma_address = (uintptr_t)sg_virt(&sg[i]); total += sg_dma_len(&sg[i]); } } else { spriv->num_sg = scsi_dma_map(cmd); for (i = 0; i < spriv->num_sg; i++) total += sg_dma_len(&sg[i]); } esp_advance_dma(): p->cur_sg++; esp_msgin_process(): spriv->cur_sg--; Thanks, Ming