From: "J. Bruce Fields" <bfields@fieldses.org>
To: David Howells <dhowells@redhat.com>
Cc: Dave Wysochanski <dwysocha@redhat.com>,
linux-nfs@vger.kernel.org, linux-cachefs@redhat.com,
Anna Schumaker <anna.schumaker@netapp.com>,
Trond Myklebust <trondmy@hammerspace.com>
Subject: Re: [Linux-cachefs] [RFC PATCH v1 0/13] Convert NFS client to new fscache-iter API
Date: Fri, 17 Jul 2020 12:18:13 -0400 [thread overview]
Message-ID: <20200717161813.GB21567@fieldses.org> (raw)
In-Reply-To: <3607831.1594999165@warthog.procyon.org.uk>
On Fri, Jul 17, 2020 at 04:19:25PM +0100, David Howells wrote:
> J. Bruce Fields <bfields@fieldses.org> wrote:
>
> > Say I had a hypothetical, err, friend, who hadn't been following that
> > FS-Cache work--could you summarize the advantages it bring us?
>
> https://lore.kernel.org/linux-nfs/159465784033.1376674.18106463693989811037.stgit@warthog.procyon.org.uk/T/#t
>
> - Makes the caching code a lot simpler (~2400 LoC removed, ~1000 LoDoc[*]
> removed at the moment from fscache, cachefiles and afs).
>
> - Stops using bmap to work out what data is cached. This isn't reliable with
> modern extend-based filesystems. A bitmap of cached granules is saved in
> an xattr instead.
>
> - Uses async DIO (kiocbs) to do I/O to/from the cache rather than using
> buffered writes (kernel_write) and pagecache snooping for read (don't ask).
>
> - A lot faster and less CPU intensive as there's no page-to-page copying.
>
> - A lot less VM pressure as it doesn't have duplicate pages in the backing
> fs that aren't really accounted right.
>
> - Uses tmpfiles+link to better handle invalidation. It will at some point
> hopefully employ linkat(AT_LINK_REPLACE) to effect cut-over on disk rather
> than unlink,link.
Thanks!--b.
> David
>
> [*] The upstream docs got ReSTified, so the doc patches I have are now useless
> and need reworking:-(.
prev parent reply other threads:[~2020-07-17 16:18 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-15 15:10 [RFC PATCH v1 0/13] Convert NFS client to new fscache-iter API Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 01/13] NFS: Clean up nfs_readpage() and nfs_readpages() Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 02/13] NFS: In nfs_readpage() only increment NFSIOS_READPAGES when read succeeds Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 03/13] NFS: Refactor nfs_readpage() and nfs_readpage_async() to use nfs_readdesc Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 04/13] NFS: Call readpage_async_filler() from nfs_readpage_async() Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 05/13] NFS: Add nfs_pageio_complete_read() and remove nfs_readpage_async() Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 06/13] NFS: Rename readpage_async_filler() to nfs_pageio_add_page_read() Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 07/13] NFS: Convert fscache_acquire_cookie and fscache_relinquish_cookie Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 08/13] NFS: Allow nfs_async_read_completion_ops to be used by other NFS code Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 09/13] NFS: Convert nfs_readpage() and readpages() to new fscache API Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 10/13] NFS: Allow NFS use of new fscache API in build Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 11/13] NFS: Only use and unuse an fscache cookie a single time based on NFS_INO_FSCACHE Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 12/13] NFS: Convert fscache invalidation and update aux_data and i_size Dave Wysochanski
2020-07-15 15:10 ` [RFC PATCH v1 13/13] NFS: Call nfs_fscache_invalidate() when write extends the size of the file Dave Wysochanski
2020-07-17 14:25 ` [RFC PATCH v1 0/13] Convert NFS client to new fscache-iter API J. Bruce Fields
2020-07-17 15:19 ` [Linux-cachefs] " David Howells
2020-07-17 16:18 ` J. Bruce Fields [this message]
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