Re: [PATCH] nfsd: Reduce contention for the nfsd_file nf_rwsem
From: Chuck Lever III <hidden>
Date: 2021-06-22 14:52:08
On Jun 17, 2021, at 7:26 PM, trondmy@kernel.org wrote:
From: Trond Myklebust <redacted>
When flushing out the unstable file writes as part of a COMMIT call, try
to perform most of of the data writes and waits outside the semaphore.
This means that if the client is sending the COMMIT as part of a memory
reclaim operation, then it can continue performing I/O, with contention
for the lock occurring only once the data sync is finished.
Fixes: 5011af4c698a ("nfsd: Fix stable writes")
Signed-off-by: Trond Myklebust <redacted>I can see write throughput improvement now. Tested-by: Chuck Lever <redacted> This is NFSv3 against an NVMe-backed XFS export, wsize=8192: v5.13-rc6: Command line used: /home/cel/bin/iozone -M -+u -i0 -i1 -s1g -r256k -t12 -I Output is in kBytes/sec Time Resolution = 0.000001 seconds. Processor cache size set to 1024 kBytes. Processor cache line size set to 32 bytes. File stride size set to 17 * record size. Throughput test with 12 processes Each process writes a 1048576 kByte file in 256 kByte records Children see throughput for 12 initial writers = 416004.59 kB/sec Parent sees throughput for 12 initial writers = 415691.65 kB/sec Min throughput per process = 34630.36 kB/sec Max throughput per process = 34703.62 kB/sec Avg throughput per process = 34667.05 kB/sec Min xfer = 1046528.00 kB CPU Utilization: Wall time 30.239 CPU time 5.854 CPU utilization 19.36 % Children see throughput for 12 rewriters = 516605.59 kB/sec Parent sees throughput for 12 rewriters = 516530.05 kB/sec Min throughput per process = 43007.56 kB/sec Max throughput per process = 43074.50 kB/sec Avg throughput per process = 43050.47 kB/sec Min xfer = 1047040.00 kB CPU utilization: Wall time 24.347 CPU time 5.882 CPU utilization 24.16 % v5.13-rc6 + Trond's patch: Command line used: /home/cel/bin/iozone -M -+u -i0 -i1 -s1g -r256k -t12 -I Output is in kBytes/sec Time Resolution = 0.000001 seconds. Processor cache size set to 1024 kBytes. Processor cache line size set to 32 bytes. File stride size set to 17 * record size. Throughput test with 12 processes Each process writes a 1048576 kByte file in 256 kByte records Children see throughput for 12 initial writers = 434971.09 kB/sec Parent sees throughput for 12 initial writers = 434649.13 kB/sec Min throughput per process = 36209.41 kB/sec Max throughput per process = 36287.55 kB/sec Avg throughput per process = 36247.59 kB/sec Min xfer = 1046528.00 kB CPU Utilization: Wall time 28.920 CPU time 5.705 CPU utilization 19.73 % Children see throughput for 12 rewriters = 544700.37 kB/sec Parent sees throughput for 12 rewriters = 544623.91 kB/sec Min throughput per process = 45320.82 kB/sec Max throughput per process = 45456.07 kB/sec Avg throughput per process = 45391.70 kB/sec Min xfer = 1045504.00 kB CPU utilization: Wall time 23.071 CPU time 5.708 CPU utilization 24.74 %
quoted hunk ↗ jump to hunk
--- fs/nfsd/vfs.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-)diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index 15adf1f6ab21..46485c04740d 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c@@ -1123,6 +1123,19 @@ nfsd_write(struct svc_rqst *rqstp, struct svc_fh *fhp, loff_t offset,} #ifdef CONFIG_NFSD_V3 +static int +nfsd_filemap_write_and_wait_range(struct nfsd_file *nf, loff_t offset, + loff_t end) +{ + struct address_space *mapping = nf->nf_file->f_mapping; + int ret = filemap_fdatawrite_range(mapping, offset, end); + + if (ret) + return ret; + filemap_fdatawait_range_keep_errors(mapping, offset, end); + return 0; +} + /* * Commit all pending writes to stable storage. *@@ -1153,10 +1166,11 @@ nfsd_commit(struct svc_rqst *rqstp, struct svc_fh *fhp,if (err) goto out; if (EX_ISSYNC(fhp->fh_export)) { - int err2; + int err2 = nfsd_filemap_write_and_wait_range(nf, offset, end); down_write(&nf->nf_rwsem); - err2 = vfs_fsync_range(nf->nf_file, offset, end, 0); + if (!err2) + err2 = vfs_fsync_range(nf->nf_file, offset, end, 0); switch (err2) { case 0: nfsd_copy_boot_verifier(verf, net_generic(nf->nf_net, -- 2.31.1
-- Chuck Lever