| Message ID | 20241108173236.1382366-1-dhowells@redhat.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | netfs: Read performance improvements and "single-blob" support | expand |
On Fri, 08 Nov 2024 17:32:01 +0000, David Howells wrote: > This set of patches is primarily about two things: improving read > performance and supporting monolithic single-blob objects that have to be > read/written as such (e.g. AFS directory contents). The implementation of > the two parts is interwoven as each makes the other possible. > > READ PERFORMANCE > ================ > > [...] Applied to the vfs-6.14.netfs branch of the vfs/vfs.git tree. Patches in the vfs-6.14.netfs branch should appear in linux-next soon. Please report any outstanding bugs that were missed during review in a new review to the original patch series allowing us to drop it. It's encouraged to provide Acked-bys and Reviewed-bys even though the patch has now been applied. If possible patch trailers will be updated. Note that commit hashes shown below are subject to change due to rebase, trailer updates or similar. If in doubt, please check the listed branch. tree: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git branch: vfs-6.14.netfs [01/33] kheaders: Ignore silly-rename files https://git.kernel.org/vfs/vfs/c/3033d243b97c [02/33] netfs: Remove call to folio_index() https://git.kernel.org/vfs/vfs/c/f709cec9dc52 [03/33] netfs: Fix a few minor bugs in netfs_page_mkwrite() https://git.kernel.org/vfs/vfs/c/07a80742a52b [04/33] netfs: Remove unnecessary references to pages https://git.kernel.org/vfs/vfs/c/53f5f31a1549 [05/33] netfs: Use a folio_queue allocation and free functions https://git.kernel.org/vfs/vfs/c/1d044b4cb3e9 [06/33] netfs: Add a tracepoint to log the lifespan of folio_queue structs https://git.kernel.org/vfs/vfs/c/7583f643f714 [07/33] netfs: Abstract out a rolling folio buffer implementation https://git.kernel.org/vfs/vfs/c/2029a747a14d [08/33] netfs: Make netfs_advance_write() return size_t https://git.kernel.org/vfs/vfs/c/34961bbe07a5 [09/33] netfs: Split retry code out of fs/netfs/write_collect.c https://git.kernel.org/vfs/vfs/c/8816207a3e26 [10/33] netfs: Drop the error arg from netfs_read_subreq_terminated() https://git.kernel.org/vfs/vfs/c/44c5114bb155 [11/33] netfs: Drop the was_async arg from netfs_read_subreq_terminated() https://git.kernel.org/vfs/vfs/c/3c8a83f74e0e [12/33] netfs: Don't use bh spinlock https://git.kernel.org/vfs/vfs/c/5c962f9982cd [13/33] afs: Don't use mutex for I/O operation lock https://git.kernel.org/vfs/vfs/c/244059f6472c [14/33] afs: Fix EEXIST error returned from afs_rmdir() to be ENOTEMPTY https://git.kernel.org/vfs/vfs/c/10e890507ed5 [15/33] afs: Fix directory format encoding struct https://git.kernel.org/vfs/vfs/c/c8f34615191c [16/33] netfs: Remove some extraneous directory invalidations https://git.kernel.org/vfs/vfs/c/ab143ef48b3b [17/33] cachefiles: Add some subrequest tracepoints https://git.kernel.org/vfs/vfs/c/46599823a281 [18/33] cachefiles: Add auxiliary data trace https://git.kernel.org/vfs/vfs/c/499c9d489d7b [19/33] afs: Add more tracepoints to do with tracking validity https://git.kernel.org/vfs/vfs/c/606d920396fd [20/33] netfs: Add functions to build/clean a buffer in a folio_queue https://git.kernel.org/vfs/vfs/c/823f8d570db5 [21/33] netfs: Add support for caching single monolithic objects such as AFS dirs https://git.kernel.org/vfs/vfs/c/5ae8e69c119a [22/33] afs: Make afs_init_request() get a key if not given a file https://git.kernel.org/vfs/vfs/c/bfeb953ddf0b [23/33] afs: Use netfslib for directories https://git.kernel.org/vfs/vfs/c/2b6bae4ca558 [24/33] afs: Use netfslib for symlinks, allowing them to be cached https://git.kernel.org/vfs/vfs/c/a16c68c66f52 [25/33] afs: Eliminate afs_read https://git.kernel.org/vfs/vfs/c/b84e275b6da2 [26/33] afs: Fix cleanup of immediately failed async calls https://git.kernel.org/vfs/vfs/c/355d07737082 [27/33] afs: Make {Y,}FS.FetchData an asynchronous operation https://git.kernel.org/vfs/vfs/c/e31fb01515da [28/33] netfs: Change the read result collector to only use one work item https://git.kernel.org/vfs/vfs/c/1bd9011ee163 [29/33] afs: Make afs_mkdir() locally initialise a new directory's content https://git.kernel.org/vfs/vfs/c/4e93a341aec1 [30/33] afs: Use the contained hashtable to search a directory https://git.kernel.org/vfs/vfs/c/08890740b1d7 [31/33] afs: Locally initialise the contents of a new symlink on creation https://git.kernel.org/vfs/vfs/c/d4f4a6bde676 [32/33] afs: Add a tracepoint for afs_read_receive() https://git.kernel.org/vfs/vfs/c/f06ba511d8d5 [33/33] netfs: Report on NULL folioq in netfs_writeback_unlock_folios() https://git.kernel.org/vfs/vfs/c/19375843912f
Hi Christian, Steve, Willy, This set of patches is primarily about two things: improving read performance and supporting monolithic single-blob objects that have to be read/written as such (e.g. AFS directory contents). The implementation of the two parts is interwoven as each makes the other possible. READ PERFORMANCE ================ The read performance improvements are intended to speed up some loss of performance detected in cifs and to a lesser extend in afs. The problem is that we queue too many work items during the collection of read results: each individual subrequest is collected by its own work item, and then they have to interact with each other when a series of subrequests don't exactly align with the pattern of folios that are being read by the overall request. Whilst the processing of the pages covered by individual subrequests as they complete potentially allows folios to be woken in parallel and with minimum delay, it can shuffle wakeups for sequential reads out of order - and that is the most common I/O pattern. The final assessment and cleanup of an operation is then held up until the last I/O completes - and for a synchronous sequential operation, this means the bouncing around of work items just adds latency. Two changes have been made to make this work: (1) All collection is now done in a single "work item" that works progressively through the subrequests as they complete (and also dispatches retries as necessary). (2) For readahead and AIO, this work item be done on a workqueue and can run in parallel with the ultimate consumer of the data; for synchronous direct or unbuffered reads, the collection is run in the application thread and not offloaded. Functions such as smb2_readv_callback() then just tell netfslib that the subrequest has terminated; netfslib does a minimal bit of processing on the spot - stat counting and tracing mostly - and then queues/wakes up the worker. This simplifies the logic as the collector just walks sequentially through the subrequests as they complete and walks through the folios, if buffered, unlocking them as it goes. It also keeps to a minimum the amount of latency injected into the filesystem's low-level I/O handling SINGLE-BLOB OBJECT SUPPORT ========================== Single-blob objects are files for which the content of the file must be read from or written to the server in a single operation because reading them in parts may yield inconsistent results. AFS directories are an example of this as there exists the possibility that the contents are generated on the fly and would differ between reads or might change due to third party interference. Such objects will be written to and retrieved from the cache if one is present, though we allow/may need to propose multiple subrequests to do so. The important part is that read from/write to the *server* is monolithic. Single blob reading is, for the moment, fully synchronous and does result collection in the application thread and, also for the moment, the API is supplied the buffer in the form of a folio_queue chain rather than using the pagecache. AFS CHANGES =========== This series makes a number of changes to the kafs filesystem, primarily in the area of directory handling: (1) AFS's FetchData RPC reply processing is made partially asynchronous which allows the netfs_io_request's outstanding operation counter to be removed as part of reducing the collection to a single work item. (2) Directory and symlink reading are plumbed through netfslib using the single-blob object API and are now cacheable with fscache. This also allows the afs_read struct to be eliminated and netfs_io_subrequest to be used directly instead. (3) Directory and symlink content are now stored in a folio_queue buffer rather than in the pagecache. This means we don't require the RCU read lock and xarray iteration to access it, and folios won't randomly disappear under us because the VM wants them back. There are some downsides to this, though: the storage folios are no longer known to the VM, drop_caches can't flush them, the folios are not migrateable. The inode must also be marked dirty manually to get the data written to the cache in the background. (4) The vnode operation lock is changed from a mutex struct to a private lock implementation. The problem is that the lock now needs to be dropped in a separate thread and mutexes don't permit that. (5) When a new directory or symlink is created, we now initialise it locally and mark it valid rather than downloading it (we know what it's likely to look like). (6) We now use the in-directory hashtable to reduce the number of entries we need to scan when doing a lookup. The edit routines have to maintain the hash chains. (7) Cancellation (e.g. by signal) of an async call after the rxrpc_call has been set up is now offloaded to the worker thread as there will be a notification from rxrpc upon completion. This avoids a double cleanup. SUPPORTING CHANGES ================== To support the above some other changes are also made: (1) A "rolling buffer" implementation is created to abstract out the two separate folio_queue chaining implementations I had (one for read and one for write). (2) Functions are provided to create/extend a buffer in a folio_queue chain and tear it down again. This is used to handle AFS directories, but could also be used to create bounce buffers for content crypto and transport crypto. (3) The was_async argument is dropped from netfs_read_subreq_terminated(). Instead we wake the read collection work item by either queuing it or waking up the app thread. (4) We don't need to use BH-excluding locks when communicating between the issuing thread and the collection thread as neither of them now run in BH context. MISCELLANY ========== Also included are some fixes from Matthew Wilcox that need to be applied first; a number of new tracepoints; a split of the netfslib write collection code to put retrying into its own file (it gets more complicated with content encryption). There are also some minor fixes AFS included, including fixing the AFS directory format struct layout, reducing some directory over-invalidation and making afs_mkdir() translate EEXIST to ENOTEMPY (which is not available on all systems the servers support). Finally, there's a patch to try and detect entry into the folio unlock function with no folio_queue structs in the buffer (which isn't allowed in the cases that can get there). This is a debugging patch, but should be minimal overhead. The patches can also be found here: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=netfs-writeback CHANGES ======= ver #4) - Fix abandonment of folios that are contributed to by a failed read subreq (such as from an interrupted op). - In afs, fix handling of failure between the directory/symlink content buffer being allocated and reading into it (thereby making it appear valid). ver #3) - In afs, fix a number of issues in asynchronous FetchData handling. - In afs, fix a signedness issue in an error check dir editing. - To afs, add a patch to fix handling of interruption by a signal whilst an async call is being set up. ver #2) - Handle that we might be in RCU pathwalk in afs_get_link(). - Fix double-call of afs_put_operation() in async FetchData. - Don't set ->mapping on directory and symlink folios as they're not in the pagecache. - Add an afs patch to search the directory's hash table on lookup. - Add an afs patch to preset the contents of a new symlink on creation. - Add an afs patch to add a tracepoint in the async FetchData response processing. - Add a patch to report if a NULL folio_queue pointer is seen in netfs_writeback_unlock_folios(). Thanks, David David Howells (30): kheaders: Ignore silly-rename files netfs: Use a folio_queue allocation and free functions netfs: Add a tracepoint to log the lifespan of folio_queue structs netfs: Abstract out a rolling folio buffer implementation netfs: Make netfs_advance_write() return size_t netfs: Split retry code out of fs/netfs/write_collect.c netfs: Drop the error arg from netfs_read_subreq_terminated() netfs: Drop the was_async arg from netfs_read_subreq_terminated() netfs: Don't use bh spinlock afs: Don't use mutex for I/O operation lock afs: Fix EEXIST error returned from afs_rmdir() to be ENOTEMPTY afs: Fix directory format encoding struct netfs: Remove some extraneous directory invalidations cachefiles: Add some subrequest tracepoints cachefiles: Add auxiliary data trace afs: Add more tracepoints to do with tracking validity netfs: Add functions to build/clean a buffer in a folio_queue netfs: Add support for caching single monolithic objects such as AFS dirs afs: Make afs_init_request() get a key if not given a file afs: Use netfslib for directories afs: Use netfslib for symlinks, allowing them to be cached afs: Eliminate afs_read afs: Fix cleanup of immediately failed async calls afs: Make {Y,}FS.FetchData an asynchronous operation netfs: Change the read result collector to only use one work item afs: Make afs_mkdir() locally initialise a new directory's content afs: Use the contained hashtable to search a directory afs: Locally initialise the contents of a new symlink on creation afs: Add a tracepoint for afs_read_receive() netfs: Report on NULL folioq in netfs_writeback_unlock_folios() Matthew Wilcox (Oracle) (3): netfs: Remove call to folio_index() netfs: Fix a few minor bugs in netfs_page_mkwrite() netfs: Remove unnecessary references to pages fs/9p/vfs_addr.c | 8 +- fs/afs/Makefile | 1 + fs/afs/callback.c | 4 +- fs/afs/dir.c | 804 +++++++++++++++--------------- fs/afs/dir_edit.c | 383 ++++++++------ fs/afs/dir_search.c | 227 +++++++++ fs/afs/file.c | 260 +++++----- fs/afs/fs_operation.c | 113 ++++- fs/afs/fsclient.c | 62 +-- fs/afs/inode.c | 140 +++++- fs/afs/internal.h | 143 ++++-- fs/afs/main.c | 2 +- fs/afs/mntpt.c | 22 +- fs/afs/rotate.c | 4 +- fs/afs/rxrpc.c | 37 +- fs/afs/super.c | 4 +- fs/afs/validation.c | 31 +- fs/afs/vlclient.c | 1 + fs/afs/write.c | 16 +- fs/afs/xdr_fs.h | 2 +- fs/afs/yfsclient.c | 49 +- fs/cachefiles/io.c | 4 + fs/cachefiles/xattr.c | 9 +- fs/ceph/addr.c | 13 +- fs/netfs/Makefile | 5 +- fs/netfs/buffered_read.c | 276 ++++------ fs/netfs/buffered_write.c | 41 +- fs/netfs/direct_read.c | 80 +-- fs/netfs/direct_write.c | 10 +- fs/netfs/internal.h | 36 +- fs/netfs/main.c | 6 +- fs/netfs/misc.c | 163 +++--- fs/netfs/objects.c | 21 +- fs/netfs/read_collect.c | 708 +++++++++++++++----------- fs/netfs/read_pgpriv2.c | 35 +- fs/netfs/read_retry.c | 209 ++++---- fs/netfs/read_single.c | 195 ++++++++ fs/netfs/rolling_buffer.c | 225 +++++++++ fs/netfs/stats.c | 4 +- fs/netfs/write_collect.c | 278 ++--------- fs/netfs/write_issue.c | 239 ++++++++- fs/netfs/write_retry.c | 233 +++++++++ fs/nfs/fscache.c | 6 +- fs/nfs/fscache.h | 3 +- fs/smb/client/cifssmb.c | 12 +- fs/smb/client/file.c | 3 +- fs/smb/client/smb2ops.c | 2 +- fs/smb/client/smb2pdu.c | 14 +- include/linux/folio_queue.h | 12 +- include/linux/netfs.h | 55 +- include/linux/rolling_buffer.h | 61 +++ include/trace/events/afs.h | 210 +++++++- include/trace/events/cachefiles.h | 13 +- include/trace/events/netfs.h | 98 ++-- kernel/gen_kheaders.sh | 1 + lib/kunit_iov_iter.c | 4 +- 56 files changed, 3646 insertions(+), 1951 deletions(-) create mode 100644 fs/afs/dir_search.c create mode 100644 fs/netfs/read_single.c create mode 100644 fs/netfs/rolling_buffer.c create mode 100644 fs/netfs/write_retry.c create mode 100644 include/linux/rolling_buffer.h