From patchwork Thu Feb 17 22:33:22 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Trond Myklebust X-Patchwork-Id: 12750701 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 48DB5C433F5 for ; Thu, 17 Feb 2022 22:39:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343926AbiBQWju (ORCPT ); Thu, 17 Feb 2022 17:39:50 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:36322 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343922AbiBQWju (ORCPT ); Thu, 17 Feb 2022 17:39:50 -0500 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 88FD1811B9 for ; Thu, 17 Feb 2022 14:39:34 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id CD5B4CE30B8 for ; Thu, 17 Feb 2022 22:39:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1A594C340F1 for ; Thu, 17 Feb 2022 22:39:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1645137571; bh=BbcYAjEyo+JiQOEWtlHT5A2N2TSllu9LC6ANfoao19k=; h=From:To:Subject:Date:In-Reply-To:References:From; b=r54Zw0Z+TKicuqsfVj2SVU11ipPFM8BCnA/GosGg7Tm49JpSZ7RWFLHnaGTHlxOys fL/4JMFX3GphV9tsmj78ZvMCIde4G/86ZPRF9djDgsg8ZOu0hP6pmoRCuyU7ptbFLi 4v5Sm/NlGAYVuVhO8B+M1T6D+oR6p8ponkk/YxhG9oKOpeKKylZDwbrtEZweV7ICvi AjumKW7F2vbpmhMJIhWV51zICjZzgXP2zV8IRwIsB+EkvqRAwcV5YDp8e0DuwwQGc8 gKPM6rWK9jc5uEZ3xhyJc4ub0qHtvgDMmYfVAJfq76a3MhT8MyR9ttdJ9+oxIz70wW 7xCET/X2V4YwQ== From: trondmy@kernel.org To: linux-nfs@vger.kernel.org Subject: [PATCH v4 4/5] NFS: Improve heuristic for readdirplus Date: Thu, 17 Feb 2022 17:33:22 -0500 Message-Id: <20220217223323.696173-5-trondmy@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220217223323.696173-4-trondmy@kernel.org> References: <20220217223323.696173-1-trondmy@kernel.org> <20220217223323.696173-2-trondmy@kernel.org> <20220217223323.696173-3-trondmy@kernel.org> <20220217223323.696173-4-trondmy@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org From: Trond Myklebust The heuristic for readdirplus is designed to try to detect 'ls -l' and similar patterns. It does so by looking for cache hit/miss patterns in both the attribute cache and in the dcache of the files in a given directory, and then sets a flag for the readdirplus code to interpret. The problem with this approach is that a single attribute or dcache miss can cause the NFS code to force a refresh of the attributes for the entire set of files contained in the directory. To be able to make a more nuanced decision, let's sample the number of hits and misses in the set of open directory descriptors. That allows us to set thresholds at which we start preferring READDIRPLUS over regular READDIR, or at which we start to force a re-read of the remaining readdir cache using READDIRPLUS. Signed-off-by: Trond Myklebust --- fs/nfs/dir.c | 77 +++++++++++++++++++++++++----------------- fs/nfs/inode.c | 4 +-- fs/nfs/internal.h | 4 +-- fs/nfs/nfstrace.h | 1 - include/linux/nfs_fs.h | 5 +-- 5 files changed, 53 insertions(+), 38 deletions(-) diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index 43a559b34f4a..cd57df004789 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -87,8 +87,7 @@ alloc_nfs_open_dir_context(struct inode *dir) nfs_set_cache_invalid(dir, NFS_INO_INVALID_DATA | NFS_INO_REVAL_FORCED); - list_add(&ctx->list, &nfsi->open_files); - clear_bit(NFS_INO_FORCE_READDIR, &nfsi->flags); + list_add_tail_rcu(&ctx->list, &nfsi->open_files); spin_unlock(&dir->i_lock); return ctx; } @@ -98,9 +97,9 @@ alloc_nfs_open_dir_context(struct inode *dir) static void put_nfs_open_dir_context(struct inode *dir, struct nfs_open_dir_context *ctx) { spin_lock(&dir->i_lock); - list_del(&ctx->list); + list_del_rcu(&ctx->list); spin_unlock(&dir->i_lock); - kfree(ctx); + kfree_rcu(ctx, rcu_head); } /* @@ -567,7 +566,6 @@ static int nfs_readdir_xdr_filler(struct nfs_readdir_descriptor *desc, /* We requested READDIRPLUS, but the server doesn't grok it */ if (error == -ENOTSUPP && desc->plus) { NFS_SERVER(inode)->caps &= ~NFS_CAP_READDIRPLUS; - clear_bit(NFS_INO_ADVISE_RDPLUS, &NFS_I(inode)->flags); desc->plus = arg.plus = false; goto again; } @@ -617,51 +615,57 @@ int nfs_same_file(struct dentry *dentry, struct nfs_entry *entry) return 1; } -static -bool nfs_use_readdirplus(struct inode *dir, struct dir_context *ctx) +#define NFS_READDIR_CACHE_USAGE_THRESHOLD (8UL) + +static bool nfs_use_readdirplus(struct inode *dir, struct dir_context *ctx, + unsigned int cache_hits, + unsigned int cache_misses) { if (!nfs_server_capable(dir, NFS_CAP_READDIRPLUS)) return false; - if (test_and_clear_bit(NFS_INO_ADVISE_RDPLUS, &NFS_I(dir)->flags)) - return true; - if (ctx->pos == 0) + if (ctx->pos == 0 || + cache_hits + cache_misses > NFS_READDIR_CACHE_USAGE_THRESHOLD) return true; return false; } /* - * This function is called by the lookup and getattr code to request the + * This function is called by the getattr code to request the * use of readdirplus to accelerate any future lookups in the same * directory. */ -void nfs_advise_use_readdirplus(struct inode *dir) +void nfs_readdir_record_entry_cache_hit(struct inode *dir) { struct nfs_inode *nfsi = NFS_I(dir); + struct nfs_open_dir_context *ctx; - if (nfs_server_capable(dir, NFS_CAP_READDIRPLUS) && - !list_empty(&nfsi->open_files)) - set_bit(NFS_INO_ADVISE_RDPLUS, &nfsi->flags); + if (nfs_server_capable(dir, NFS_CAP_READDIRPLUS)) { + list_for_each_entry_rcu (ctx, &nfsi->open_files, list) + atomic_inc(&ctx->cache_hits); + } } /* * This function is mainly for use by nfs_getattr(). * * If this is an 'ls -l', we want to force use of readdirplus. - * Do this by checking if there is an active file descriptor - * and calling nfs_advise_use_readdirplus, then forcing a - * cache flush. */ -void nfs_force_use_readdirplus(struct inode *dir) +void nfs_readdir_record_entry_cache_miss(struct inode *dir) { struct nfs_inode *nfsi = NFS_I(dir); + struct nfs_open_dir_context *ctx; - if (nfs_server_capable(dir, NFS_CAP_READDIRPLUS) && - !list_empty(&nfsi->open_files)) { - set_bit(NFS_INO_ADVISE_RDPLUS, &nfsi->flags); - set_bit(NFS_INO_FORCE_READDIR, &nfsi->flags); + if (nfs_server_capable(dir, NFS_CAP_READDIRPLUS)) { + list_for_each_entry_rcu (ctx, &nfsi->open_files, list) + atomic_inc(&ctx->cache_misses); } } +static void nfs_readdir_record_dcache_miss(struct inode *dir) +{ + nfs_readdir_record_entry_cache_miss(dir); +} + static void nfs_prime_dcache(struct dentry *parent, struct nfs_entry *entry, unsigned long dir_verifier) @@ -1101,6 +1105,18 @@ static int uncached_readdir(struct nfs_readdir_descriptor *desc) return status; } +#define NFS_READDIR_CACHE_MISS_THRESHOLD (16UL) + +static void nfs_readdir_handle_cache_misses(struct inode *inode, + struct nfs_readdir_descriptor *desc, + pgoff_t page_index, + unsigned int cache_misses) +{ + if (desc->ctx->pos != 0 && + cache_misses > NFS_READDIR_CACHE_MISS_THRESHOLD) + invalidate_mapping_pages(inode->i_mapping, page_index + 1, -1); +} + /* The file offset position represents the dirent entry number. A last cookie cache takes care of the common case of reading the whole directory. @@ -1112,6 +1128,7 @@ static int nfs_readdir(struct file *file, struct dir_context *ctx) struct nfs_inode *nfsi = NFS_I(inode); struct nfs_open_dir_context *dir_ctx = file->private_data; struct nfs_readdir_descriptor *desc; + unsigned int cache_hits, cache_misses; pgoff_t page_index; int res; @@ -1137,7 +1154,6 @@ static int nfs_readdir(struct file *file, struct dir_context *ctx) goto out; desc->file = file; desc->ctx = ctx; - desc->plus = nfs_use_readdirplus(inode, ctx); desc->page_index_max = -1; spin_lock(&file->f_lock); @@ -1150,6 +1166,8 @@ static int nfs_readdir(struct file *file, struct dir_context *ctx) desc->page_fill_misses = dir_ctx->page_fill_misses; nfs_set_dtsize(desc, dir_ctx->dtsize); memcpy(desc->verf, dir_ctx->verf, sizeof(desc->verf)); + cache_hits = atomic_xchg(&dir_ctx->cache_hits, 0); + cache_misses = atomic_xchg(&dir_ctx->cache_misses, 0); spin_unlock(&file->f_lock); if (desc->eof) { @@ -1157,9 +1175,8 @@ static int nfs_readdir(struct file *file, struct dir_context *ctx) goto out_free; } - if (test_and_clear_bit(NFS_INO_FORCE_READDIR, &nfsi->flags) && - list_is_singular(&nfsi->open_files)) - invalidate_mapping_pages(inode->i_mapping, page_index + 1, -1); + desc->plus = nfs_use_readdirplus(inode, ctx, cache_hits, cache_misses); + nfs_readdir_handle_cache_misses(inode, desc, page_index, cache_misses); do { res = readdir_search_pagecache(desc); @@ -1178,7 +1195,6 @@ static int nfs_readdir(struct file *file, struct dir_context *ctx) break; } if (res == -ETOOSMALL && desc->plus) { - clear_bit(NFS_INO_ADVISE_RDPLUS, &nfsi->flags); nfs_zap_caches(inode); desc->page_index = 0; desc->plus = false; @@ -1602,7 +1618,7 @@ nfs_lookup_revalidate_dentry(struct inode *dir, struct dentry *dentry, nfs_set_verifier(dentry, dir_verifier); /* set a readdirplus hint that we had a cache miss */ - nfs_force_use_readdirplus(dir); + nfs_readdir_record_dcache_miss(dir); ret = 1; out: nfs_free_fattr(fattr); @@ -1659,7 +1675,6 @@ nfs_do_lookup_revalidate(struct inode *dir, struct dentry *dentry, nfs_mark_dir_for_revalidate(dir); goto out_bad; } - nfs_advise_use_readdirplus(dir); goto out_valid; } @@ -1866,7 +1881,7 @@ struct dentry *nfs_lookup(struct inode *dir, struct dentry * dentry, unsigned in goto out; /* Notify readdir to use READDIRPLUS */ - nfs_force_use_readdirplus(dir); + nfs_readdir_record_dcache_miss(dir); no_entry: res = d_splice_alias(inode, dentry); diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c index f9fc506ebb29..1bef81f5373a 100644 --- a/fs/nfs/inode.c +++ b/fs/nfs/inode.c @@ -789,7 +789,7 @@ static void nfs_readdirplus_parent_cache_miss(struct dentry *dentry) if (!nfs_server_capable(d_inode(dentry), NFS_CAP_READDIRPLUS)) return; parent = dget_parent(dentry); - nfs_force_use_readdirplus(d_inode(parent)); + nfs_readdir_record_entry_cache_miss(d_inode(parent)); dput(parent); } @@ -800,7 +800,7 @@ static void nfs_readdirplus_parent_cache_hit(struct dentry *dentry) if (!nfs_server_capable(d_inode(dentry), NFS_CAP_READDIRPLUS)) return; parent = dget_parent(dentry); - nfs_advise_use_readdirplus(d_inode(parent)); + nfs_readdir_record_entry_cache_hit(d_inode(parent)); dput(parent); } diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h index 2de7c56a1fbe..46dc97b65661 100644 --- a/fs/nfs/internal.h +++ b/fs/nfs/internal.h @@ -366,8 +366,8 @@ extern struct nfs_client *nfs_init_client(struct nfs_client *clp, const struct nfs_client_initdata *); /* dir.c */ -extern void nfs_advise_use_readdirplus(struct inode *dir); -extern void nfs_force_use_readdirplus(struct inode *dir); +extern void nfs_readdir_record_entry_cache_hit(struct inode *dir); +extern void nfs_readdir_record_entry_cache_miss(struct inode *dir); extern unsigned long nfs_access_cache_count(struct shrinker *shrink, struct shrink_control *sc); extern unsigned long nfs_access_cache_scan(struct shrinker *shrink, diff --git a/fs/nfs/nfstrace.h b/fs/nfs/nfstrace.h index 45a310b586ce..3672f6703ee7 100644 --- a/fs/nfs/nfstrace.h +++ b/fs/nfs/nfstrace.h @@ -36,7 +36,6 @@ #define nfs_show_nfsi_flags(v) \ __print_flags(v, "|", \ - { BIT(NFS_INO_ADVISE_RDPLUS), "ADVISE_RDPLUS" }, \ { BIT(NFS_INO_STALE), "STALE" }, \ { BIT(NFS_INO_ACL_LRU_SET), "ACL_LRU_SET" }, \ { BIT(NFS_INO_INVALIDATING), "INVALIDATING" }, \ diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h index 9e5fc29723c2..e21bd9452d27 100644 --- a/include/linux/nfs_fs.h +++ b/include/linux/nfs_fs.h @@ -101,6 +101,8 @@ struct nfs_open_context { struct nfs_open_dir_context { struct list_head list; + atomic_t cache_hits; + atomic_t cache_misses; unsigned long attr_gencount; __be32 verf[NFS_DIR_VERIFIER_SIZE]; __u64 dir_cookie; @@ -110,6 +112,7 @@ struct nfs_open_dir_context { unsigned int dtsize; signed char duped; bool eof; + struct rcu_head rcu_head; }; /* @@ -274,13 +277,11 @@ struct nfs4_copy_state { /* * Bit offsets in flags field */ -#define NFS_INO_ADVISE_RDPLUS (0) /* advise readdirplus */ #define NFS_INO_STALE (1) /* possible stale inode */ #define NFS_INO_ACL_LRU_SET (2) /* Inode is on the LRU list */ #define NFS_INO_INVALIDATING (3) /* inode is being invalidated */ #define NFS_INO_PRESERVE_UNLINKED (4) /* preserve file if removed while open */ #define NFS_INO_FSCACHE (5) /* inode can be cached by FS-Cache */ -#define NFS_INO_FORCE_READDIR (7) /* force readdirplus */ #define NFS_INO_LAYOUTCOMMIT (9) /* layoutcommit required */ #define NFS_INO_LAYOUTCOMMITTING (10) /* layoutcommit inflight */ #define NFS_INO_LAYOUTSTATS (11) /* layoutstats inflight */