From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D9D1E1E5B63 for ; Mon, 14 Jul 2025 13:14:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752498870; cv=none; b=Y3EODZ59AySsE9m+i0BSP5OV4hmQAU4RqAbcwreRfK3lFiPB1iVASpn/GMsabNMUPNzv9kCSj36x52jvUd/dvIVVDxlcXxc2hDJdRPOF5eenBqee+Qsm9I/gGf1RfTuvbxzH7EzSQDoIBDHCkxLK3NBc/EaCQFFh/fx4y36cmjQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752498870; c=relaxed/simple; bh=hvt0efFcZUmBUEKELYY5Yv8pZ6UyKKCGpgzjrdXv/S0=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=mvzaH2+DT0LChrAy/9hkWWSxFxxD18akOXEEALPdE9kXAVWBwrTfMOhKmFBrCybjfngm0mElpmKcJEw9dKjHT2uhHw1E0XGNlb/s3oJsFq+FShxElPOKcKewyfezP+prfXAkTpE7GqDcEnCp4rihEpxIf68zycglSFSCu5CLR9U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KtcjbjzS; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KtcjbjzS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EC065C4CEF4; Mon, 14 Jul 2025 13:14:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752498870; bh=hvt0efFcZUmBUEKELYY5Yv8pZ6UyKKCGpgzjrdXv/S0=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=KtcjbjzSno7yUx8gSdOYmJnyVT4isqY0Ve/J9GhSmVox6PloR9EzbkV5z9vTydAal NzNGSWy6BQmE1+nhukYVCtUuONL6yG7AD6cEYgXL+p6OYsooDZ1JFMaLVRV4lSqzUu he3fz//6ZX9vWcoXzMmYR87qRjowN7VY3HR/4JX+oYHeSHYTjmg9Gy3o3ybzYdVWni VhqiV5cS+4rqcqsdu1Anq50KPpEcK8Bq+cSPKivJCSc3Wjkfnp0FUC2cxdVbDf8b0m SIhFU/quScR3bcvppy8zdkgiCXXCCGu1oM6pMSsmAazONZIXSBY12uIKJjyXNJcuq9 gOaSSy28uT/fg== Message-ID: Subject: Re: [PATCH 4/4] NFS: use a hash table for delegation lookup From: Jeff Layton To: Christoph Hellwig , Trond Myklebust Cc: Anna Schumaker , linux-nfs@vger.kernel.org Date: Mon, 14 Jul 2025 09:14:27 -0400 In-Reply-To: <20250714111651.1565055-5-hch@lst.de> References: <20250714111651.1565055-1-hch@lst.de> <20250714111651.1565055-5-hch@lst.de> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 0OX6MYPtv76hka8lW4mnRmZqqx3UtfHX/hF/zH24Gj7A6sYKYLCU3YrI2Ogiu7/ksKcl7goQjpvtV 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can become pretty large, and can become even > larger when increasing the delegation watermark. >=20 > Add a hash table to speed up the delegation lookup, sized as a fraction > of the delegation watermark. >=20 > Signed-off-by: Christoph Hellwig > --- > fs/nfs/client.c | 23 +++++++++++++++++++---- > fs/nfs/delegation.c | 15 +++++++++++++-- > fs/nfs/delegation.h | 3 +++ > include/linux/nfs_fs_sb.h | 2 ++ > 4 files changed, 37 insertions(+), 6 deletions(-) >=20 > diff --git a/fs/nfs/client.c b/fs/nfs/client.c > index f55188928f67..94684a476dd8 100644 > --- a/fs/nfs/client.c > +++ b/fs/nfs/client.c > @@ -994,6 +994,7 @@ static DEFINE_IDA(s_sysfs_ids); > struct nfs_server *nfs_alloc_server(void) > { > struct nfs_server *server; > + int delegation_buckets, i; > =20 > server =3D kzalloc(sizeof(struct nfs_server), GFP_KERNEL); > if (!server) > @@ -1019,11 +1020,18 @@ struct nfs_server *nfs_alloc_server(void) > atomic_set(&server->active, 0); > atomic_long_set(&server->nr_active_delegations, 0); > =20 > + delegation_buckets =3D roundup_pow_of_two(nfs_delegation_watermark / 16= ); > + server->delegation_hash_mask =3D delegation_buckets - 1; > + server->delegation_hash_table =3D kmalloc_array(delegation_buckets, > + sizeof(*server->delegation_hash_table), GFP_KERNEL); > + if (!server->delegation_hash_table) > + goto out_free_server; > + for (i =3D 0; i < delegation_buckets; i++) > + INIT_HLIST_HEAD(&server->delegation_hash_table[i]); > + This is going to get created for any mount, even v3 ones. It might be better to only bother with this for v4 mounts. Maybe do this in nfs4_server_common_setup() instead? Also, I wonder if you'd be better off using the rhashtable infrastructure instead of adding a fixed-size one? The number of delegations in flight is very workload-dependent, so a resizeable hashtable may be a better option. > server->io_stats =3D nfs_alloc_iostats(); > - if (!server->io_stats) { > - kfree(server); > - return NULL; > - } > + if (!server->io_stats) > + goto out_free_delegation_hash; > =20 > server->change_attr_type =3D NFS4_CHANGE_TYPE_IS_UNDEFINED; > =20 > @@ -1036,6 +1044,12 @@ struct nfs_server *nfs_alloc_server(void) > rpc_init_wait_queue(&server->uoc_rpcwaitq, "NFS UOC"); > =20 > return server; > + > +out_free_delegation_hash: > + kfree(server->delegation_hash_table); > +out_free_server: > + kfree(server); > + return NULL; > } > EXPORT_SYMBOL_GPL(nfs_alloc_server); > =20 > @@ -1044,6 +1058,7 @@ static void delayed_free(struct rcu_head *p) > struct nfs_server *server =3D container_of(p, struct nfs_server, rcu); > =20 > nfs_free_iostats(server->io_stats); > + kfree(server->delegation_hash_table); > kfree(server); > } > =20 > diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c > index 621b635d1c56..ca830ceb466e 100644 > --- a/fs/nfs/delegation.c > +++ b/fs/nfs/delegation.c > @@ -27,9 +27,16 @@ > =20 > #define NFS_DEFAULT_DELEGATION_WATERMARK (15000U) > =20 > -static unsigned nfs_delegation_watermark =3D NFS_DEFAULT_DELEGATION_WATE= RMARK; > +unsigned nfs_delegation_watermark =3D NFS_DEFAULT_DELEGATION_WATERMARK; > module_param_named(delegation_watermark, nfs_delegation_watermark, uint,= 0644); > =20 > +static struct hlist_head *nfs_delegation_hash(struct nfs_server *server, > + const struct nfs_fh *fhandle) > +{ > + return server->delegation_hash_table + > + (nfs_fhandle_hash(fhandle) & server->delegation_hash_mask); > +} > + > static void __nfs_free_delegation(struct nfs_delegation *delegation) > { > put_cred(delegation->cred); > @@ -367,6 +374,7 @@ nfs_detach_delegation_locked(struct nfs_inode *nfsi, > spin_unlock(&delegation->lock); > return NULL; > } > + hlist_del_init_rcu(&delegation->hash); > list_del_rcu(&delegation->super_list); > delegation->inode =3D NULL; > rcu_assign_pointer(nfsi->delegation, NULL); > @@ -529,6 +537,8 @@ int nfs_inode_set_delegation(struct inode *inode, con= st struct cred *cred, > spin_unlock(&inode->i_lock); > =20 > list_add_tail_rcu(&delegation->super_list, &server->delegations); > + hlist_add_head_rcu(&delegation->hash, > + nfs_delegation_hash(server, &NFS_I(inode)->fh)); > rcu_assign_pointer(nfsi->delegation, delegation); > delegation =3D NULL; > =20 > @@ -1166,11 +1176,12 @@ static struct inode * > nfs_delegation_find_inode_server(struct nfs_server *server, > const struct nfs_fh *fhandle) > { > + struct hlist_head *head =3D nfs_delegation_hash(server, fhandle); > struct nfs_delegation *delegation; > struct super_block *freeme =3D NULL; > struct inode *res =3D NULL; > =20 > - list_for_each_entry_rcu(delegation, &server->delegations, super_list) { > + hlist_for_each_entry_rcu(delegation, head, hash) { > spin_lock(&delegation->lock); > if (delegation->inode !=3D NULL && > !test_bit(NFS_DELEGATION_REVOKED, &delegation->flags) && > diff --git a/fs/nfs/delegation.h b/fs/nfs/delegation.h > index 8ff5ab9c5c25..9f1fb9b39c43 100644 > --- a/fs/nfs/delegation.h > +++ b/fs/nfs/delegation.h > @@ -14,6 +14,7 @@ > * NFSv4 delegation > */ > struct nfs_delegation { > + struct hlist_node hash; > struct list_head super_list; > const struct cred *cred; > struct inode *inode; > @@ -123,4 +124,6 @@ static inline int nfs_have_delegated_mtime(struct ino= de *inode) > NFS_DELEGATION_FLAG_TIME); > } > =20 > +extern unsigned nfs_delegation_watermark; > + > #endif > diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h > index fe930d685780..88212306fd87 100644 > --- a/include/linux/nfs_fs_sb.h > +++ b/include/linux/nfs_fs_sb.h > @@ -256,6 +256,8 @@ struct nfs_server { > struct list_head layouts; > struct list_head delegations; > atomic_long_t nr_active_delegations; > + unsigned int delegation_hash_mask; > + struct hlist_head *delegation_hash_table; > struct list_head ss_copies; > struct list_head ss_src_copies; > =20 --=20 Jeff Layton