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Subject: [PATCH v1 00/11] Put struct nfsd4_copy on a diet
From:   Chuck Lever <chuck.lever@oracle.com>
To:     linux-nfs@vger.kernel.org
Date:   Fri, 22 Jul 2022 16:18:56 -0400
Message-ID: <165852076926.11403.44005570813790008.stgit@manet.1015granger.net>
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Precedence: bulk

While testing NFSD for-next, I noticed svc_generic_init_request()
was an unexpected hot spot on NFSv4 workloads. Drilling into the
perf report, it shows that the hot path in there is:

1208         memset(rqstp->rq_argp, 0, procp->pc_argsize);
1209         memset(rqstp->rq_resp, 0, procp->pc_ressize);

For an NFSv4 COMPOUND,

	procp->pc_argsize = sizeof(nfsd4_compoundargs),

struct nfsd4_compoundargs on my system is more than 17KB! This is
due to the size of the iops field:

	struct nfsd4_op                 iops[8];

Each struct nfsd4_op contains a union of the arguments for each
NFSv4 operation. Each argument is typically less than 128 bytes
except that struct nfsd4_copy and struct nfsd4_copy_notify are both
larger than 2KB each.

I'm not yet totally convinced this series never orphans memory, but
it does reduce the size of nfsd4_compoundargs to just over 4KB. This
is still due to struct nfsd4_copy being almost 500 bytes. I don't
see more low-hanging fruit there, though.

---

Chuck Lever (11):
      NFSD: Shrink size of struct nfsd4_copy_notify
      NFSD: Shrink size of struct nfsd4_copy
      NFSD: Reorder the fields in struct nfsd4_op
      NFSD: Make nfs4_put_copy() static
      NFSD: Make boolean fields in struct nfsd4_copy into atomic bit flags
      NFSD: Refactor nfsd4_cleanup_inter_ssc() (1/2)
      NFSD: Refactor nfsd4_cleanup_inter_ssc() (2/2)
      NFSD: Refactor nfsd4_do_copy()
      NFSD: Remove kmalloc from nfsd4_do_async_copy()
      NFSD: Add nfsd4_send_cb_offload()
      NFSD: Move copy offload callback arguments into a separate structure


 fs/nfsd/nfs4callback.c |  37 +++++----
 fs/nfsd/nfs4proc.c     | 165 +++++++++++++++++++++--------------------
 fs/nfsd/nfs4xdr.c      |  30 +++++---
 fs/nfsd/state.h        |   1 -
 fs/nfsd/xdr4.h         |  54 ++++++++++----
 5 files changed, 163 insertions(+), 124 deletions(-)

--
Chuck Lever