| Message ID | 20220227231227.9038-1-trondmy@kernel.org (mailing list archive) |
|---|---|
| Headers | show |
| Series | Readdir improvements | expand |
On 27 Feb 2022, at 18:12, trondmy@kernel.org wrote: > From: Trond Myklebust <trond.myklebust@hammerspace.com> > > The current NFS readdir code will always try to maximise the amount of > readahead it performs on the assumption that we can cache anything that > isn't immediately read by the process. > There are several cases where this assumption breaks down, including > when the 'ls -l' heuristic kicks in to try to force use of readdirplus > as a batch replacement for lookup/getattr. > > This series also implement Ben's page cache filter to ensure that we can > improve the ability to share cached data between processes that are > reading the same directory at the same time, and to avoid live-locks > when the directory is simultaneously changing. > > -- > v2: Remove reset of dtsize when NFS_INO_FORCE_READDIR is set > v3: Avoid excessive window shrinking in uncached_readdir case > v4: Track 'ls -l' cache hit/miss statistics > Improved algorithm for falling back to uncached readdir > Skip readdirplus when files are being written to > v5: bugfixes > Skip readdirplus when the acdirmax/acregmax values are low > Request a full XDR buffer when doing READDIRPLUS > v6: Add tracing > Don't have lookup request readdirplus when it won't help > v7: Implement Ben's page cache filter > Reduce the use of uncached readdir > Change indexing of the page cache to improve seekdir() performance. > v8: Reduce the page cache overhead by shrinking the cookie hashvalue size > Incorporate other feedback from Anna, Ben and Neil > Fix nfs2/3_decode_dirent return values > Fix the change attribute value set in nfs_readdir_page_get_next() > v9: Address bugs that were hit when testing with large directories > Misc cleanups Hi Trond, thanks for all this work! I went through these from your testing branch (612896ec5a4e) rather than the posting. If it pleases, these can all get marked with my Reviewed-by: Benjamin Coddington <bcodding@redhat.com> and/or Tested-by: Benjamin Coddington <bcodding@redhat.com> .. except for 25/27, which is missing from the testing branch. As I replied to 23/27, I don't understand how the page index hashing is going to help out the re-export seekdir case, I think it might make it worse, and I think its unnecessary extra complication. I did test extensively total directory listing correctness, and it appears to me that you are correct, we are not regressing. We're in a similar place as before. I think we can be even more correct with directory verifiers or post-op updates with GETATTR in the READDIR compound for very little cost, but I've already made those arguments a few weeks ago. Thanks again, Ben
From: Trond Myklebust <trond.myklebust@hammerspace.com> The current NFS readdir code will always try to maximise the amount of readahead it performs on the assumption that we can cache anything that isn't immediately read by the process. There are several cases where this assumption breaks down, including when the 'ls -l' heuristic kicks in to try to force use of readdirplus as a batch replacement for lookup/getattr. This series also implement Ben's page cache filter to ensure that we can improve the ability to share cached data between processes that are reading the same directory at the same time, and to avoid live-locks when the directory is simultaneously changing. -- v2: Remove reset of dtsize when NFS_INO_FORCE_READDIR is set v3: Avoid excessive window shrinking in uncached_readdir case v4: Track 'ls -l' cache hit/miss statistics Improved algorithm for falling back to uncached readdir Skip readdirplus when files are being written to v5: bugfixes Skip readdirplus when the acdirmax/acregmax values are low Request a full XDR buffer when doing READDIRPLUS v6: Add tracing Don't have lookup request readdirplus when it won't help v7: Implement Ben's page cache filter Reduce the use of uncached readdir Change indexing of the page cache to improve seekdir() performance. v8: Reduce the page cache overhead by shrinking the cookie hashvalue size Incorporate other feedback from Anna, Ben and Neil Fix nfs2/3_decode_dirent return values Fix the change attribute value set in nfs_readdir_page_get_next() v9: Address bugs that were hit when testing with large directories Misc cleanups Trond Myklebust (27): NFS: Return valid errors from nfs2/3_decode_dirent() NFS: constify nfs_server_capable() and nfs_have_writebacks() NFS: Trace lookup revalidation failure NFS: Initialise the readdir verifier as best we can in nfs_opendir() NFS: Use kzalloc() to avoid initialising the nfs_open_dir_context NFS: Calculate page offsets algorithmically NFS: Store the change attribute in the directory page cache NFS: Don't re-read the entire page cache to find the next cookie NFS: Don't advance the page pointer unless the page is full NFS: Adjust the amount of readahead performed by NFS readdir NFS: If the cookie verifier changes, we must invalidate the page cache NFS: Simplify nfs_readdir_xdr_to_array() NFS: Reduce use of uncached readdir NFS: Improve heuristic for readdirplus NFS: Don't ask for readdirplus unless it can help nfs_getattr() NFSv4: Ask for a full XDR buffer of readdir goodness NFS: Readdirplus can't help lookup for case insensitive filesystems NFS: Don't request readdirplus when revalidation was forced NFS: Add basic readdir tracing NFS: Trace effects of readdirplus on the dcache NFS: Trace effects of the readdirplus heuristic NFS: Clean up page array initialisation/free NFS: Convert readdir page cache to use a cookie based index NFS: Fix up forced readdirplus NFS: Remove unnecessary cache invalidations for directories NFS: Optimise away the previous cookie field NFS: Cache all entries in the readdirplus reply fs/nfs/Kconfig | 4 + fs/nfs/dir.c | 602 ++++++++++++++++++++++++---------------- fs/nfs/inode.c | 46 ++- fs/nfs/internal.h | 4 +- fs/nfs/nfs2xdr.c | 3 +- fs/nfs/nfs3xdr.c | 29 +- fs/nfs/nfs4proc.c | 2 - fs/nfs/nfs4xdr.c | 7 +- fs/nfs/nfstrace.h | 123 +++++++- include/linux/nfs_fs.h | 19 +- include/linux/nfs_xdr.h | 3 +- 11 files changed, 532 insertions(+), 310 deletions(-)