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Tue, 13 Jul 2021 10:36:30 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 4450D1E0373; Tue, 13 Jul 2021 12:36:30 +0200 (CEST) From: Jan Kara To: Andrew Morton Cc: , Michael Stapelberg , Wu Fengguang , Jan Kara Subject: [PATCH 1/5] writeback: Track number of inodes under writeback Date: Tue, 13 Jul 2021 12:36:25 +0200 Message-Id: <20210713103630.19490-1-jack@suse.cz> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210713103347.8364-1-jack@suse.cz> References: <20210713103347.8364-1-jack@suse.cz> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3585; h=from:subject; bh=Zeq+cUy1mIFc1qc2HQSxZ+fSxvX//gzG+ErjN7SAgIk=; b=owEBbQGS/pANAwAIAZydqgc/ZEDZAcsmYgBg7Wyo04ZaFftLHzPfiiZ8fXJElaqNpl1ONjU9hAaE Hiz7x6mJATMEAAEIAB0WIQSrWdEr1p4yirVVKBycnaoHP2RA2QUCYO1sqAAKCRCcnaoHP2RA2bpyCA DewDbg9DjGHdZC7vgORYCokOvWnpQaTfKYWB4T++8vysy+KkNVuWLBWpUkdTOYSc00dt4h2r1a6gd+ HmzoBLQhi/Ucst4EsGjhZhTDcyWbpuwFqNJr3EeZ3VoO9507p8E4YrPzMK4cYOGDFgNbi6F6mw3hl7 bWPXREZkj1wkyL6rb8Aqg2rJ/UcI2sEBvsg3dhzum+cQfCCmz+a8T0/kr2LJXuYbl70FYYdc1jSzSU hL0N/m4MMSrawJrXAD3omD2uIkxnOuBrJr9e6oWKfidBGLP1++9B9ywV9d9La7R/4o+OhX86P2ADok FxAmz10Q3xZeiaXRtw8JK2M2s9I/aR X-Developer-Key: i=jack@suse.cz; a=openpgp; fpr=93C6099A142276A28BBE35D815BC833443038D8C Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=Ukq8ntmV; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b="obp0XC/c"; spf=pass (imf22.hostedemail.com: domain of jack@suse.cz designates 195.135.220.28 as permitted sender) smtp.mailfrom=jack@suse.cz; dmarc=none X-Stat-Signature: k5ugrupcrckxu57obwqiwux74wgx9999 X-Rspamd-Queue-Id: 801E1191D X-Rspamd-Server: rspam01 X-HE-Tag: 1626172591-191303 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Track number of inodes under writeback for each bdi_writeback structure. We will use this to decide whether wb does any IO and so we can estimate its writeback throughput. In principle we could use number of pages under writeback (WB_WRITEBACK counter) for this however normal percpu counter reads are too inaccurate for our purposes and summing the counter is too expensive. Signed-off-by: Jan Kara --- fs/fs-writeback.c | 5 +++++ include/linux/backing-dev-defs.h | 1 + mm/backing-dev.c | 1 + mm/page-writeback.c | 22 ++++++++++++++++++++-- 4 files changed, 27 insertions(+), 2 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 06d04a74ab6c..54300f4d38af 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -406,6 +406,11 @@ static bool inode_do_switch_wbs(struct inode *inode, inc_wb_stat(new_wb, WB_WRITEBACK); } =20 + if (mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK)) { + atomic_dec(&old_wb->writeback_inodes); + atomic_inc(&new_wb->writeback_inodes); + } + wb_get(new_wb); =20 /* diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev= -defs.h index 1d7edad9914f..06fb8e13f6bc 100644 --- a/include/linux/backing-dev-defs.h +++ b/include/linux/backing-dev-defs.h @@ -116,6 +116,7 @@ struct bdi_writeback { struct list_head b_dirty_time; /* time stamps are dirty */ spinlock_t list_lock; /* protects the b_* lists */ =20 + atomic_t writeback_inodes; /* number of inodes under writeback */ struct percpu_counter stat[NR_WB_STAT_ITEMS]; =20 unsigned long congested; /* WB_[a]sync_congested flags */ diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 271f2ca862c8..1bf16b1eed47 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -293,6 +293,7 @@ static int wb_init(struct bdi_writeback *wb, struct b= acking_dev_info *bdi, INIT_LIST_HEAD(&wb->b_dirty_time); spin_lock_init(&wb->list_lock); =20 + atomic_set(&wb->writeback_inodes, 0); wb->bw_time_stamp =3D jiffies; wb->balanced_dirty_ratelimit =3D INIT_BW; wb->dirty_ratelimit =3D INIT_BW; diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 9f63548f247c..e1aa1c9d8e36 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -2731,6 +2731,16 @@ int clear_page_dirty_for_io(struct page *page) } EXPORT_SYMBOL(clear_page_dirty_for_io); =20 +static void wb_inode_writeback_start(struct bdi_writeback *wb) +{ + atomic_inc(&wb->writeback_inodes); +} + +static void wb_inode_writeback_end(struct bdi_writeback *wb) +{ + atomic_dec(&wb->writeback_inodes); +} + int test_clear_page_writeback(struct page *page) { struct address_space *mapping =3D page_mapping(page); @@ -2752,6 +2762,9 @@ int test_clear_page_writeback(struct page *page) =20 dec_wb_stat(wb, WB_WRITEBACK); __wb_writeout_inc(wb); + if (!mapping_tagged(mapping, + PAGECACHE_TAG_WRITEBACK)) + wb_inode_writeback_end(wb); } } =20 @@ -2794,8 +2807,13 @@ int __test_set_page_writeback(struct page *page, b= ool keep_write) PAGECACHE_TAG_WRITEBACK); =20 xas_set_mark(&xas, PAGECACHE_TAG_WRITEBACK); - if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT) - inc_wb_stat(inode_to_wb(inode), WB_WRITEBACK); + if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT) { + struct bdi_writeback *wb =3D inode_to_wb(inode); + + inc_wb_stat(wb, WB_WRITEBACK); + if (!on_wblist) + wb_inode_writeback_start(wb); + } =20 /* * We can come through here when swapping anonymous --=20 2.26.2