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h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=b6hAzcK9a6ZsHa0Mk3iI21Eqpc+IV+6ztwUn4mhqw/zL741FObJn7o/U9JxPSucFA SEs+LS9B625yiZiRfHBLry2rSnVIcwt334tzjVqkWVwgBsNZDdhpSWaH5YoM+Re3XR MVE+EarzW3FoEwNNGRRa6truUMvxx/+8yivIASe4= Date: Tue, 14 Oct 2025 18:03:12 -0700 From: Andrew Morton To: Kundan Kumar Cc: jaegeuk@kernel.org, chao@kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, miklos@szeredi.hu, agruenba@redhat.com, trondmy@kernel.org, anna@kernel.org, willy@infradead.org, mcgrof@kernel.org, clm@meta.com, david@fromorbit.com, amir73il@gmail.com, axboe@kernel.dk, hch@lst.de, ritesh.list@gmail.com, djwong@kernel.org, dave@stgolabs.net, wangyufei@vivo.com, linux-f2fs-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, gfs2@lists.linux.dev, linux-nfs@vger.kernel.org, linux-mm@kvack.org, gost.dev@samsung.com, anuj20.g@samsung.com, vishak.g@samsung.com, joshi.k@samsung.com Subject: Re: [PATCH v2 00/16] Parallelizing filesystem writeback Message-Id: <20251014180312.6917d7bd5681d4c8ca356691@linux-foundation.org> In-Reply-To: <20251014120845.2361-1-kundan.kumar@samsung.com> References: <20251014120845.2361-1-kundan.kumar@samsung.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: irsi8xbxy9dcnpb5996ox8otuwksrq6c X-Rspamd-Queue-Id: ED2A440012 X-Rspamd-Server: rspam09 X-HE-Tag: 1760490195-440433 X-HE-Meta: U2FsdGVkX1/ph/cV95F111AipvQ9rrM2ail5bhyM0J24j0cIlDferBPU5zjt8548i5k0vd41X2524JZauopVAwtZERzwLXdsVpnkA8O9xX3UsJcvcGDJ5YA0Yij8pZ8eGoIBL4f9nE+GekHOMeNCJeX4B5XxaxJvZxnKh5ID38+7C5k2xWNc95kuJGSKZ28s8xADHPkFRKTqa9UicEseXmHoBYV1c7RJZg639fUVfnZtR8XJVJZkWYAZLa5drUPX9ZTA0TSrEbP4/qtCznMDpPNob7/tgnWLeGAI3IbUlQQX22O6u1oFQ0IRUfTGhERl8AFR7oaxvKXF/uC26rJSLt6Vb7q6gKAqMWxKeZ9HBOgvkkwLto+cfk4YFMYgBIu7D9lKHnJ0qoL1jWKu4MH22Y5i/wCOLLl5Krm23W88iuhNMwjcDXJq5WOucYSr79zl3fLJYUAezC2+035VnPHXCOlXJ7ixjnGbZ2UcMRcfLASqxBGvO+Dj5ojKoIyt+M+Q+9rU1QTlIAgdDNuuR9GvxrYRzr/erT7Bi4F+Rj73znAMHM6dBNFZjPNOZmj1KgEfwSGwAxn8HinCftPHO8MTvoMR6guYiDWqMPZ7urAR1LzGzlVNQAs0wb5NLb+9BiRS3rdSVPTExyRPgFFB9dR96TUF2b3kNEaluApbqPQLISmpm6G+BHSrKO78Q1bexd4jH8WZqguyoujiEQOCHYB4yu5yswzHDEXL8MOdrHublnqgYCOFq4t66dVIg6HHLfvXHEWLO5SKGruwz8CrBIBBGFyw/FhQ8XIfw2I6Ic5bVduovIj0LmevpOKHfFZb1WjFsfkPqVrolryESysj2E8vi91P0zMaX1ba999Iv/n4ZPIVoKfND3eUPZ+DjbESUdjZthMLQnUbOP1lbQ+Qf8+aLOszaBzNGPwVw/zKS1vgspuvcGe2ugS2z+/cHrxb5I+SGEwMxEck9AUuE0Ex0Ej FnaqeLiO zQbrN74IizKsb69ZomJAsyRiOOcUKhOXPOlgZxhlb2V1kLNGGiEzjLQN5/yO4G3I6h6Yll6YK/p/exZ4q8PHpaYWOkhF+PNwCyVkakdzM622ZDtd/JV8KSzVYj0phx2lmmzqS5XF3t7+XqeMQ/cE2ZMAWSC6D9S02qod1ghbH375r5kT34GRar4pSWQV6k/jt8nCrir4I3Dh6oK93VizvVm+sblhGoWrxYVTOFtmsGIUcV38/RAF2Rr2VEkD35QjqEklWfCR1AqxRI1RBcKo+Jo/VTN7VcMzSUf9pb+fJMAzQV/XPHOR6tS8mysvLRyYIdlryUSaKh6J0VG6T4VtrxQ68Pw== 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: List-Subscribe: List-Unsubscribe: On Tue, 14 Oct 2025 17:38:29 +0530 Kundan Kumar wrote: > Currently, pagecache writeback is performed by a single thread. Inodes > are added to a dirty list, and delayed writeback is triggered. The single > writeback thread then iterates through the dirty inode list, and executes > the writeback. > > This series parallelizes the writeback by allowing multiple writeback > contexts per backing device (bdi). These writeback contexts are executed > as separate, independent threads, improving overall parallelism. Inodes > are distributed to these threads and are flushed in parallel. > > ... > > IOPS and throughput > =================== > With the affinity to allocation group we see significant improvement in > XFS when we write to multiple files in different directories(AGs). > > Performance gains: > A) Workload 12 files each of 1G in 12 directories(AGs) - numjobs = 12 > - NVMe device BM1743 SSD > Base XFS : 243 MiB/s > Parallel Writeback XFS : 759 MiB/s (+212%) > > - NVMe device PM9A3 SSD > Base XFS : 368 MiB/s > Parallel Writeback XFS : 1634 MiB/s (+344%) > > B) Workload 6 files each of 20G in 6 directories(AGs) - numjobs = 6 > - NVMe device BM1743 SSD > Base XFS : 305 MiB/s > Parallel Writeback XFS : 706 MiB/s (+131%) > > - NVMe device PM9A3 SSD > Base XFS : 315 MiB/s > Parallel Writeback XFS : 990 MiB/s (+214%) > > Filesystem fragmentation > ======================== > We also see that there is no increase in filesystem fragmentation > Number of extents per file: > A) Workload 6 files each 1G in single directory(AG) - numjobs = 1 > Base XFS : 17 > Parallel Writeback XFS : 17 > > B) Workload 12 files each of 1G to 12 directories(AGs)- numjobs = 12 > Base XFS : 166593 > Parallel Writeback XFS : 161554 > > C) Workload 6 files each of 20G to 6 directories(AGs) - numjobs = 6 > Base XFS : 3173716 > Parallel Writeback XFS : 3364984 Nice results. Is testing planned for other filesystems?