From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0ABB3247280; Thu, 29 Jan 2026 00:44:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769647446; cv=none; b=sVoV+V6t/0wND2w2tKrWs0yTlZSA7o3b+90BZpjgbt96HW3wjjp188gWg/qediHqpUQqdX7u1m/HL7ylyBGqeqPTYhxWhj2LLOTeBCYHkzcVO5YN+vJ5NmPMCPUw7s6I5enyncdGaPvXtvtZauuqXfqu3rEG0ymd7T2v5HeQMHA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769647446; c=relaxed/simple; bh=du+Chat2KKUjWi9KMstZ4LpJLC7xzl/p+SbRJ5Wo4Zk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=SlsrajPAlbhJX77TAeO/ACPLhXrRtRGEIRbixcH0QdvhoP492Bx612OkBPKwqKm9b40m+vnvOGGqFfzTjzTOLJ2DL6yplfFx09pduuaWWEFx1FYlvZKK3zIXeZw324T24jeD7st7/O5N2fWeqgCCHXSYRSYLzuMoVELWmiXfaPU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NI7vmT9C; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="NI7vmT9C" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6D83AC4CEF1; Thu, 29 Jan 2026 00:44:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769647445; bh=du+Chat2KKUjWi9KMstZ4LpJLC7xzl/p+SbRJ5Wo4Zk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=NI7vmT9CRQFjO8mg1hFcsnq+/zwLSuSJG5XMxheGO3KEhe7eyZQdBY7VfZb+1nCGe R9woJsKNb3DCaoOzYBoG/vEBz6HwICn+EunyGgRGlbqhx2UAmewFUiSdIJZmHZJDFz MbCo2VP9ytTKwTlIePkAuci6DO7CYMhxir91QvsfJQhVaIk5fHM81UQd3OdOdJiYj2 uaTuRP+cbyJ6/d24vJgrmraoutXjgUHHfsutaqzIJ5i9nteMYtT7QxBzSxQ3papiPZ WihvCxMaKaukGT/qogCcD6Vtgg0RXFDPE/CFY9yjx4v20buEFL4QTRGtIr0HCTv4Oz 7XF37cwgR/2FA== Date: Wed, 28 Jan 2026 16:44:04 -0800 From: "Darrick J. Wong" To: Kundan Kumar Cc: viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, 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, dave@stgolabs.net, cem@kernel.org, wangyufei@vivo.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-xfs@vger.kernel.org, gost.dev@samsung.com, anuj20.g@samsung.com, vishak.g@samsung.com, joshi.k@samsung.com Subject: Re: [PATCH v3 3/6] xfs: add per-inode AG prediction map and dirty-AG bitmap Message-ID: <20260129004404.GA7712@frogsfrogsfrogs> References: <20260116100818.7576-1-kundan.kumar@samsung.com> <20260116100818.7576-4-kundan.kumar@samsung.com> Precedence: bulk X-Mailing-List: linux-fsdevel@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: <20260116100818.7576-4-kundan.kumar@samsung.com> On Fri, Jan 16, 2026 at 03:38:15PM +0530, Kundan Kumar wrote: > Add per-inode structures to track predicted AGs of dirty folios using > an xarray and bitmap. This enables efficient identification of AGs > involved in writeback. > > Signed-off-by: Kundan Kumar > Signed-off-by: Anuj Gupta > --- > fs/xfs/xfs_icache.c | 27 +++++++++++++++++++++++++++ > fs/xfs/xfs_inode.h | 5 +++++ > 2 files changed, 32 insertions(+) > > diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c > index e44040206851..f97aa6d66271 100644 > --- a/fs/xfs/xfs_icache.c > +++ b/fs/xfs/xfs_icache.c > @@ -80,6 +80,25 @@ static inline xa_mark_t ici_tag_to_mark(unsigned int tag) > return XFS_PERAG_BLOCKGC_MARK; > } > > +static int xfs_inode_init_ag_bitmap(struct xfs_inode *ip) > +{ > + unsigned int bits = ip->i_mount->m_sb.sb_agcount; > + unsigned int nlongs; > + > + xa_init_flags(&ip->i_ag_pmap, XA_FLAGS_LOCK_IRQ); This increases the size of struct xfs_inode by 40 bytes... > + ip->i_ag_dirty_bitmap = NULL; > + ip->i_ag_dirty_bits = bits; > + > + if (!bits) > + return 0; > + > + nlongs = BITS_TO_LONGS(bits); > + ip->i_ag_dirty_bitmap = kcalloc(nlongs, sizeof(unsigned long), > + GFP_NOFS); ...and there could be hundreds or thousands of AGs for each filesystem. That's a lot of kernel memory to handle this prediction stuff, and I"m not even sure what ag_dirty_bitmap does yet. > + > + return ip->i_ag_dirty_bitmap ? 0 : -ENOMEM; > +} > + > /* > * Allocate and initialise an xfs_inode. > */ > @@ -131,6 +150,8 @@ xfs_inode_alloc( > ip->i_next_unlinked = NULLAGINO; > ip->i_prev_unlinked = 0; > > + xfs_inode_init_ag_bitmap(ip); Unchecked return value??? > + > return ip; > } > > @@ -194,6 +215,12 @@ xfs_inode_free( > ip->i_ino = 0; > spin_unlock(&ip->i_flags_lock); > > + /* free xarray contents (values are immediate packed ints) */ > + xa_destroy(&ip->i_ag_pmap); > + kfree(ip->i_ag_dirty_bitmap); > + ip->i_ag_dirty_bitmap = NULL; > + ip->i_ag_dirty_bits = 0; > + > __xfs_inode_free(ip); > } > > diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h > index bd6d33557194..dee449168605 100644 > --- a/fs/xfs/xfs_inode.h > +++ b/fs/xfs/xfs_inode.h > @@ -99,6 +99,11 @@ typedef struct xfs_inode { > spinlock_t i_ioend_lock; > struct work_struct i_ioend_work; > struct list_head i_ioend_list; > + > + /* AG prediction map: pgoff_t -> packed u32 */ What about blocksize < pagesize filesystems? Which packed agno do you associate with the pgoff_t? Also, do you have an xarray entry for each pgoff_t in a large folio? --D > + struct xarray i_ag_pmap; > + unsigned long *i_ag_dirty_bitmap; > + unsigned int i_ag_dirty_bits; > } xfs_inode_t; > > static inline bool xfs_inode_on_unlinked_list(const struct xfs_inode *ip) > -- > 2.25.1 > >