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Thu, 21 Mar 2024 18:07:04 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id rgb8JUh3/GXaOQAAD6G6ig (envelope-from ); Thu, 21 Mar 2024 18:07:04 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 422C6A0806; Thu, 21 Mar 2024 19:07:04 +0100 (CET) Date: Thu, 21 Mar 2024 19:07:04 +0100 From: Jan Kara To: Kemeng Shi Cc: Jan Kara , akpm@linux-foundation.org, tj@kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, willy@infradead.org, bfoster@redhat.com, dsterba@suse.com, mjguzik@gmail.com, dhowells@redhat.com, peterz@infradead.org Subject: Re: [PATCH 0/6] Improve visibility of writeback Message-ID: <20240321180704.lqmtdmd5tzsbuyyu@quack3> References: <20240320110222.6564-1-shikemeng@huaweicloud.com> <20240320172240.7buswiv7zj2m5odg@quack3> <44e3b910-8b52-5583-f8a9-37105bf5e5b6@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <44e3b910-8b52-5583-f8a9-37105bf5e5b6@huaweicloud.com> X-Spam-Score: 4.30 X-Spamd-Result: default: False [4.30 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; BAYES_SPAM(5.10)[100.00%]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_GOOD(-0.10)[text/plain]; NEURAL_HAM_LONG(-1.00)[-1.000]; RCVD_COUNT_THREE(0.00)[3]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; RCPT_COUNT_TWELVE(0.00)[13]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:email]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; MID_RHS_NOT_FQDN(0.50)[]; FREEMAIL_CC(0.00)[suse.cz,linux-foundation.org,kernel.org,kvack.org,vger.kernel.org,infradead.org,redhat.com,suse.com,gmail.com]; RCVD_TLS_ALL(0.00)[] X-Spam-Level: **** Authentication-Results: smtp-out2.suse.de; none X-Spam-Flag: NO On Thu 21-03-24 16:12:52, Kemeng Shi wrote: > on 3/21/2024 1:22 AM, Jan Kara wrote: > > On Wed 20-03-24 19:02:16, Kemeng Shi wrote: > >> This series tries to improve visilibity of writeback. Patch 1 make > >> /sys/kernel/debug/bdi/xxx/stats show writeback info of whole bdi > >> instead of only writeback info in root cgroup. Patch 2 add a new > >> debug file /sys/kernel/debug/bdi/xxx/wb_stats to show per wb writeback > >> info. Patch 4 add wb_monitor.py to monitor basic writeback info > >> of running system, more info could be added on demand. Rest patches > >> are some random cleanups. More details can be found in respective > >> patches. Thanks! > >> > >> Following domain hierarchy is tested: > >> global domain (320G) > >> / \ > >> cgroup domain1(10G) cgroup domain2(10G) > >> | | > >> bdi wb1 wb2 > >> > >> /* all writeback info of bdi is successfully collected */ > >> # cat /sys/kernel/debug/bdi/252:16/stats: > >> BdiWriteback: 448 kB > >> BdiReclaimable: 1303904 kB > >> BdiDirtyThresh: 189914124 kB > >> DirtyThresh: 195337564 kB > >> BackgroundThresh: 32516508 kB > >> BdiDirtied: 3591392 kB > >> BdiWritten: 2287488 kB > >> BdiWriteBandwidth: 322248 kBps > >> b_dirty: 0 > >> b_io: 0 > >> b_more_io: 2 > >> b_dirty_time: 0 > >> bdi_list: 1 > >> state: 1 > >> > >> /* per wb writeback info is collected */ > >> # cat /sys/kernel/debug/bdi/252:16/wb_stats: > >> cat wb_stats > >> WbCgIno: 1 > >> WbWriteback: 0 kB > >> WbReclaimable: 0 kB > >> WbDirtyThresh: 0 kB > >> WbDirtied: 0 kB > >> WbWritten: 0 kB > >> WbWriteBandwidth: 102400 kBps > >> b_dirty: 0 > >> b_io: 0 > >> b_more_io: 0 > >> b_dirty_time: 0 > >> state: 1 > >> WbCgIno: 4284 > >> WbWriteback: 448 kB > >> WbReclaimable: 818944 kB > >> WbDirtyThresh: 3096524 kB > >> WbDirtied: 2266880 kB > >> WbWritten: 1447936 kB > >> WbWriteBandwidth: 214036 kBps > >> b_dirty: 0 > >> b_io: 0 > >> b_more_io: 1 > >> b_dirty_time: 0 > >> state: 5 > >> WbCgIno: 4325 > >> WbWriteback: 224 kB > >> WbReclaimable: 819392 kB > >> WbDirtyThresh: 2920088 kB > >> WbDirtied: 2551808 kB > >> WbWritten: 1732416 kB > >> WbWriteBandwidth: 201832 kBps > >> b_dirty: 0 > >> b_io: 0 > >> b_more_io: 1 > >> b_dirty_time: 0 > >> state: 5 > >> > >> /* monitor writeback info */ > >> # ./wb_monitor.py 252:16 -c > >> writeback reclaimable dirtied written avg_bw > >> 252:16_1 0 0 0 0 102400 > >> 252:16_4284 672 820064 9230368 8410304 685612 > >> 252:16_4325 896 819840 10491264 9671648 652348 > >> 252:16 1568 1639904 19721632 18081952 1440360 > >> > >> > >> writeback reclaimable dirtied written avg_bw > >> 252:16_1 0 0 0 0 102400 > >> 252:16_4284 672 820064 9230368 8410304 685612 > >> 252:16_4325 896 819840 10491264 9671648 652348 > >> 252:16 1568 1639904 19721632 18081952 1440360 > >> ... > > > > So I'm wondering: Are you implementing this just because this looks > > interesting or do you have a real need for the functionality? Why? > Hi Jan, I added debug files to test change in [1] which changes the way how > dirty background threshold of wb is calculated. Without debug files, we could > only monitor writeback to imply that threshold is corrected. > In current patchset, debug info has not included dirty background threshold yet, > I will add it when discution of calculation of dirty background threshold in [1] > is done. > The wb_monitor.py is suggested by Tejun in [2] to improve visibility of writeback. > The script is more convenient than trace to monitor writeback behavior of the running > system. Thanks for the pointer. OK, I agree this is useful so let's have a look into the code :) Honza -- Jan Kara SUSE Labs, CR