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Tue, 20 Feb 2024 12:22:47 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap2.dmz-prg2.suse.org with ESMTPSA id e26HIJeZ1GVcEgAAn2gu4w (envelope-from ); Tue, 20 Feb 2024 12:22:47 +0000 Date: Tue, 20 Feb 2024 13:22:10 +0100 From: David Sterba To: Naohiro Aota Cc: linux-btrfs@vger.kernel.org, wangyugui@e16-tech.com, clm@meta.com, hch@lst.de Subject: Re: [PATCH v3] btrfs: introduce offload_csum_mode to tweak checksum offloading behavior Message-ID: <20240220122210.GD355@twin.jikos.cz> Reply-To: dsterba@suse.cz References: <8dc4a312da70bb93f042f32a75efb7ec848cc08b.1707122589.git.naohiro.aota@wdc.com> Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8dc4a312da70bb93f042f32a75efb7ec848cc08b.1707122589.git.naohiro.aota@wdc.com> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) X-Spam-Level: Authentication-Results: smtp-out2.suse.de; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=KeRUeglP; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=mdU7mZ+6 X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-4.74 / 50.00]; ARC_NA(0.00)[]; HAS_REPLYTO(0.30)[dsterba@suse.cz]; R_DKIM_ALLOW(-0.20)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; MIME_GOOD(-0.10)[text/plain]; REPLYTO_ADDR_EQ_FROM(0.00)[]; DWL_DNSWL_HI(-3.50)[suse.cz:dkim]; RCPT_COUNT_FIVE(0.00)[5]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:98:from]; RCVD_COUNT_THREE(0.00)[3]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.cz:+]; MX_GOOD(-0.01)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_ALL(0.00)[]; BAYES_HAM(-0.03)[56.17%] X-Spam-Score: -4.74 X-Rspamd-Queue-Id: 9E39D1F871 X-Spam-Flag: NO On Mon, Feb 05, 2024 at 10:01:16PM +0900, Naohiro Aota wrote: > We disable offloading checksum to workqueues and do it synchronously when > the checksum algorithm is fast. However, as reported in the link below, > RAID0 with multiple devices may suffer from the sync checksum, because > "fast checksum" is still not fast enough to catch up RAID0 writing. > > To measure the effectiveness of sync checksum and checksum offloading for > developers, it would be better to have a switch for the checksum offloading > under CONFIG_BTRFS_DEBUG hood. > > This commit introduces fs_devices->offload_csum_mode for > CONFIG_BTRFS_DEBUG, so that a btrfs developer can change the behavior by > writing to /sys/fs/btrfs//offload_csum. The default is "auto" which > is the same as the previous behavior. Or, you can set "on" or "off" (or "y" > or "n" whatever kstrtobool() accepts) to always/never offload checksum. > > More benchmark should be collected with this knob to implement a proper > criteria to enable/disable checksum offloading. > > Link: https://lore.kernel.org/linux-btrfs/20230731152223.4EFB.409509F4@e16-tech.com/ > Link: https://lore.kernel.org/linux-btrfs/p3vo3g7pqn664mhmdhlotu5dzcna6vjtcoc2hb2lsgo2fwct7k@xzaxclba5tae/ > Signed-off-by: Naohiro Aota I'm adding this to for-next.