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Inconsistencies in FSFS cache-* options

From: Julian Foad <julianfoad_at_apache.org>
Date: Thu, 16 Mar 2017 14:08:34 +0000

Stefan2 et al.:

Nodeprops caching is new in 1.10. This caused me to have a look at the
code for enabling it, and I noticed the following in FSFS (and the same
in FSX).

In subversion/libsvn_fs_fs/caching.c_at_1787000, around line 100:
> /* don't cache text deltas by default.

Wrong: the default was changed to TRUE in r1517479, and this new default
is contrary to the reasoning given in this comment.

> * Once we reconstructed the fulltexts from the deltas,
> * these deltas are rarely re-used. Therefore, only tools
> * like svnadmin will activate this to speed up operations
> * dump and verify.
> */
> *cache_txdeltas
> = svn_hash__get_bool(fs->config,
> SVN_FS_CONFIG_FSFS_CACHE_DELTAS,
> TRUE);
[...]
> /* by default, cache nodeprops: this will match pre-1.10
> * behavior where node properties caching was controlled
> * by SVN_FS_CONFIG_FSFS_CACHE_FULLTEXTS configuration option.

The default of TRUE doesn't match that behaviour, does it? To do so,
should the last argument (below) be "*cache_txdeltas" instead of "TRUE"?

> */
> *cache_nodeprops
> = svn_hash__get_bool(fs->config,
> SVN_FS_CONFIG_FSFS_CACHE_NODEPROPS,
> TRUE);

Also, the handling of these flags in mod_dav_svn (around line 990) is odd:

> svn_boolean_t
> dav_svn__get_txdelta_cache_flag(request_rec *r)
> {
> dir_conf_t *conf;
>
> conf = ap_get_module_config(r->per_dir_config, &dav_svn_module);
>
> /* txdelta caching is enabled by default. */
> return get_conf_flag(conf->txdelta_cache, TRUE);
> }
>
>
> svn_boolean_t
> dav_svn__get_fulltext_cache_flag(request_rec *r)
> {
> dir_conf_t *conf;
>
> conf = ap_get_module_config(r->per_dir_config, &dav_svn_module);
> return conf->fulltext_cache == CONF_FLAG_ON;

This construction ("==ON") means the default here is OFF, which is the
opposite of the default that FSFS would apply if we didn't pass it any
value for this flag.

> }
>
>
> svn_boolean_t
> dav_svn__get_revprop_cache_flag(request_rec *r)
> {
> dir_conf_t *conf;
>
> conf = ap_get_module_config(r->per_dir_config, &dav_svn_module);
> return conf->revprop_cache == CONF_FLAG_ON;
> }
>
> svn_boolean_t
> dav_svn__get_nodeprop_cache_flag(request_rec *r)
> {
> dir_conf_t *conf;
>
> conf = ap_get_module_config(r->per_dir_config, &dav_svn_module);
> /* node properties caching is enabled by default. */
> return get_conf_flag(conf->nodeprop_cache, FALSE);

The code here uses a default value of "FALSE", which is different from
the fsfs.conf default value (see above), and doesn't match the comment here.

> }

- Julian
Received on 2017-03-16 15:08:38 CET

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