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[209.85.208.177]) by smtp.gmail.com with ESMTPSA id 1sm4208457ljr.6.2020.08.07.13.11.55 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 07 Aug 2020 13:11:55 -0700 (PDT) Received: by mail-lj1-f177.google.com with SMTP id t23so3488607ljc.3 for ; Fri, 07 Aug 2020 13:11:55 -0700 (PDT) X-Received: by 2002:a2e:b008:: with SMTP id y8mr6135959ljk.421.1596831114811; Fri, 07 Aug 2020 13:11:54 -0700 (PDT) MIME-Version: 1.0 References: <20200807160327.GA977@redhat.com> In-Reply-To: <20200807160327.GA977@redhat.com> From: Linus Torvalds Date: Fri, 7 Aug 2020 13:11:38 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [git pull] device mapper changes for 5.9 To: Mike Snitzer Cc: dm-devel@redhat.com, linux-block , Alasdair G Kergon , Damien Le Moal , Ignat Korchagin , JeongHyeon Lee , Johannes Thumshirn , John Dorminy , Mikulas Patocka , Ming Lei , yangerkun Content-Type: text/plain; charset="UTF-8" Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Fri, Aug 7, 2020 at 9:03 AM Mike Snitzer wrote: > > - DM crypt improvement to optionally avoid async processing via > workqueues for reads and/or writes -- via "no_read_workqueue" and > "no_write_workqueue" features. This more direct IO processing > improves latency and throughput with faster storage. Avoiding > workqueue IO submission for writes (DM_CRYPT_NO_WRITE_WORKQUEUE) is > a requirement for adding zoned block device support to DM crypt. Is there a reason the async workqueue isn't removed entirely if it's not a win? Or at least made to not be the default. Now it seems to be just optionally disabled, which seems the wrong way around to me. I do not believe async crypto has ever worked or been worth it. Off-loaded crypto in the IO path, yes. Async using a workqueue? Naah. Or do I misunderstand? Linus