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Re: svn commit: r981684 - in /subversion/branches/performance/subversion/libsvn_fs_fs: caching.c fs_fs.h

From: Stefan Fuhrmann <stefanfuhrmann_at_alice-dsl.de>
Date: Tue, 03 Aug 2010 23:57:53 +0200

Blair Zajac wrote:
> On 08/02/2010 01:51 PM, stefan2_at_apache.org wrote:
>> Author: stefan2
>> Date: Mon Aug 2 20:51:35 2010
>> New Revision: 981684
>>
>> URL: http://svn.apache.org/viewvc?rev=981684&view=rev
>> Log:
>> Bring the membuffer cache to its first use for the full text cache.
>> Also, provide functions to get / set the FSFS cache configuration
>> although not all of it is supported, yet.
>>
>
> Stefan,
>
> I appreciate you working on this, I'm looking forward to using these
> improvements in production, which is why I'm closely looking at them.
Hi Blair,

I'm always open to constructive criticism.
So, tanks for your feedback!
>
>> +/* Access to the cache settings as a process-wide singleton. */
>> +static svn_fs_fs__cache_config_t *
>> +internal_get_cache_config(void)
>> +{
>> + static svn_fs_fs__cache_config_t settings =
>> + {
>> + /* default configuration:
>> + */
>> + 0x8000000, /* 128 MB for caches */
>> + 16, /* up to 16 files kept open */
>> + FALSE, /* don't cache fulltexts */
>> + FALSE, /* don't cache text deltas */
>> + FALSE /* assume multi-threaded operation */
>> + };
>> +
>> + return&settings;
>> +}
>
>
> Why not make "settings" static at file scope instead of inside this
> function? What does this function provide for us?
Just a habit of mine from the C++ world (Meyer's singleton).
But since this is a POD structure, there should be no
initialization issues. I changed it to a static variable.
>
>> +/* Access the process-global (singleton) membuffer cache. The first
>> call
>> + * will automatically allocate the cache using the current cache
>> config.
>> + * NULL will be returned if the desired cache size is 0.
>> + */
>> +static svn_membuffer_t *
>> +get_global_membuffer_cache(void)
>> +{
>> + static svn_membuffer_t *cache = NULL;
>> +
>> + apr_uint64_t cache_size = svn_fs_fs__get_cache_config()->cache_size;
>> + if (!cache&& cache_size)
>
> s/cache&&/cache &&/
This seems to be a mailer artifact. At least in my editor it shows up fine.
>
>> + {
>> + /* auto-allocate cache*/
>> + apr_allocator_t *allocator = NULL;
>> + apr_pool_t *pool = NULL;
>> +
>> + if (apr_allocator_create(&allocator))
>> + return NULL;
>> +
>> + /* ensure that a we free partially allocated data if we run OOM
>
>
> s/a we/we/
Fixed.
>> + */
>> + apr_allocator_max_free_set(allocator, 1);
>> + pool = svn_pool_create_ex(NULL, allocator);
>> +
>> + svn_cache__membuffer_cache_create
>> + (&cache,
>> + cache_size,
>> + cache_size / 16,
>> + ! svn_fs_fs__get_cache_config()->single_threaded,
>> + pool);
>> + }
> + * before the cache is complete.
>
> So the allocator is associated with this pool forever then? So it
> cannot be destroyed after
It limits the amount of *unused* memory held by the pool to 1 byte.
I extended on the commentary how that helps with certain OOM
situations.
>> + {
>> + ffd->fulltext_cache = NULL;
>> + }
>> +
>> + if (ffd->fulltext_cache&& ! no_handler)
> - ffd->fulltext_cache = NULL;
>
> s/fulltext_cache&& ! no_handler/fulltext_cache && ! no_handler
Same artifact as above.
>
>> + SVN_ERR(svn_cache__set_error_handler(ffd->fulltext_cache,
>> + warn_on_cache_errors, fs, pool));
>>
>> return SVN_NO_ERROR;
>> }
>>
>> Modified:
>> subversion/branches/performance/subversion/libsvn_fs_fs/fs_fs.h
>> URL:
>> http://svn.apache.org/viewvc/subversion/branches/performance/subversion/libsvn_fs_fs/fs_fs.h?rev=981684&r1=981683&r2=981684&view=diff
>>
>> ==============================================================================
>>
>> --- subversion/branches/performance/subversion/libsvn_fs_fs/fs_fs.h
>> (original)
>> +++ subversion/branches/performance/subversion/libsvn_fs_fs/fs_fs.h
>> Mon Aug 2 20:51:35 2010
>> @@ -523,6 +523,39 @@ svn_fs_fs__get_node_origin(const svn_fs_
>> svn_error_t *
>> svn_fs_fs__initialize_caches(svn_fs_t *fs, apr_pool_t *pool);
>>
>> +/* FSFS cache settings. It controls what caches, in what size and
>> + how they will be created. The settomgs apply for the whole process.
>
> s/settomgs/settings/
Fixed.
>
>> + */
>> +typedef struct svn_fs_fs__cache_config_t
>> +{
>> + /* total cache size in bytes. May be 0, resulting in no cache
>> being used */
>> + apr_uint64_t cache_size;
>> +
>> + /* maximum number of files kept open */
>> + apr_size_t file_handle_count;
>> +
>> + /* shall fulltexts be cached? */
>> + svn_boolean_t cache_fulltexts;
>> +
>> + /* shall text deltas be cached? */
>> + svn_boolean_t cache_txdeltas;
>> +
>> + /* is this a guaranteed single-threaded application? */
>> + svn_boolean_t single_threaded;
>> +} svn_fs_fs__cache_config_t;
>> +
>> +/* Get the current FSFS cache configuration. If it has not been set,
>> + yet, this function will return the default settings.
>
>
> s/yet,//
dito.
>
>> + */
>> +const svn_fs_fs__cache_config_t *
>> +svn_fs_fs__get_cache_config(void);
>> +
>> +/* Set the FSFS cache configuration. Please note that it may not change
>> + the actual configuration *in use*. Therefore, call it before reading
>> + data from any FSFS repo and call it only once.
>
> Should also document that this is not multi-threaded safe and does not
> protect against races, just as you do at the functions implementation.
done.
>> +void
>> +svn_fs_fs__set_cache_config(svn_fs_fs__cache_config_t *settings);
> + */
>
> Instead of
>
> svn_fs_fs__cache_config_t *settings
>
> make it const:
>
> const svn_fs_fs__cache_config_t *settings
done.
>
> Regards,
> Blair
>

-- Stefan^2.
Received on 2010-08-03 23:58:57 CEST

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