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[174.109.172.136]) by smtp.gmail.com with ESMTPSA id k11sm4118646qtu.45.2020.11.03.08.05.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Nov 2020 08:05:18 -0800 (PST) Subject: Re: [PATCH v9 30/41] btrfs: avoid async metadata checksum on ZONED mode To: Naohiro Aota , linux-btrfs@vger.kernel.org, dsterba@suse.com Cc: hare@suse.com, linux-fsdevel@vger.kernel.org References: <3434830b6fadf644c5a47eaaea6759c375b39ad7.1604065695.git.naohiro.aota@wdc.com> From: Josef Bacik Message-ID: Date: Tue, 3 Nov 2020 11:05:17 -0500 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <3434830b6fadf644c5a47eaaea6759c375b39ad7.1604065695.git.naohiro.aota@wdc.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 10/30/20 9:51 AM, Naohiro Aota wrote: > In ZONED, btrfs uses per-FS zoned_meta_io_lock to serialize the metadata > write IOs. > > Even with these serialization, write bios sent from btree_write_cache_pages > can be reordered by async checksum workers as these workers are per CPU and > not per zone. > > To preserve write BIO ordering, we can disable async metadata checksum on > ZONED. This does not result in lower performance with HDDs as a single CPU > core is fast enough to do checksum for a single zone write stream with the > maximum possible bandwidth of the device. If multiple zones are being > written simultaneously, HDD seek overhead lowers the achievable maximum > bandwidth, resulting again in a per zone checksum serialization not > affecting performance. > > Signed-off-by: Naohiro Aota Reviewed-by: Josef Bacik Thanks, Josef