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Re: svn commit: r1393211 - /subversion/trunk/subversion/libsvn_fs_fs/fs_fs.c

From: Daniel Shahaf <d.s_at_daniel.shahaf.name>
Date: Wed, 17 Oct 2012 02:01:57 +0200

stefan2_at_apache.org wrote on Tue, Oct 02, 2012 at 22:15:28 -0000:
> Author: stefan2
> Date: Tue Oct 2 22:15:28 2012
> New Revision: 1393211
>
> URL: http://svn.apache.org/viewvc?rev=1393211&view=rev
> Log:
> Empty representations are relatively frequent (1..2%) in FSFS.
> However, we can't easily distinghish them from non-empty plain
> representations because for the latter the expanded size value
> will be given as 0.
>
> This patch explicitly detects the case that a delta rep is
> actually an empty rep and should be cached as such.
>
> * subversion/libsvn_fs_fs/fs_fs.c
> (build_rep_list): determine and correct the expanded size
> (rep_read_get_baton): let the above determine the fulltext length
>
> Modified:
> subversion/trunk/subversion/libsvn_fs_fs/fs_fs.c
>
> Modified: subversion/trunk/subversion/libsvn_fs_fs/fs_fs.c
> URL: http://svn.apache.org/viewvc/subversion/trunk/subversion/libsvn_fs_fs/fs_fs.c?rev=1393211&r1=1393210&r2=1393211&view=diff
> ==============================================================================
> --- subversion/trunk/subversion/libsvn_fs_fs/fs_fs.c (original)
> +++ subversion/trunk/subversion/libsvn_fs_fs/fs_fs.c Tue Oct 2 22:15:28 2012
> @@ -4553,11 +4553,15 @@ set_cached_combined_window(svn_stringbuf
> ID, and representation REP.
> Also, set *WINDOW_P to the base window content for *LIST, if it
> could be found in cache. Otherwise, *LIST will contain the base
> - representation for the whole delta chain. */
> + representation for the whole delta chain.
> + Finally, return the expanded size of the representation in
> + *EXPANDED_SIZE. It will take care of cases where only the on-disk
> + size is known. */
> static svn_error_t *
> build_rep_list(apr_array_header_t **list,
> svn_stringbuf_t **window_p,
> struct rep_state **src_state,
> + svn_filesize_t *expanded_size,
> svn_fs_t *fs,
> representation_t *first_rep,
> apr_pool_t *pool)
> @@ -4572,10 +4576,24 @@ build_rep_list(apr_array_header_t **list
> *list = apr_array_make(pool, 1, sizeof(struct rep_state *));
> rep = *first_rep;
>
> + /* The value as stored in the data struct.
> + 0 is either for unknown length or actually zero length. */
> + *expanded_size = first_rep->expanded_size;
> while (1)
> {
> SVN_ERR(create_rep_state(&rs, &rep_args, &last_file,
> &last_revision, &rep, fs, pool));
> +
> + /* Unknown size or empty representation?
> + That implies the this being the first iteration.
> + Usually size equals on-disk size, except for empty,
> + compressed representations (delta, size = 4).
> + Please note that for all non-empty deltas have
> + a 4-byte header _plus_ some data. */
> + if (*expanded_size == 0)
> + if (! rep_args->is_delta || first_rep->size != 4)
> + *expanded_size = first_rep->size;

Is it correct to perform this assignment for delta reps with size!=4 ?

It seems odd that this check is in the loop but uses first_rep. Should
this check move out of the loop, or use rep.size instead of
first_rep->size?

> +
> SVN_ERR(get_cached_combined_window(window_p, rs, &is_cached, pool));
> if (is_cached)
> {
> @@ -4632,12 +4650,16 @@ rep_read_get_baton(struct rep_read_baton
> b->md5_checksum_ctx = svn_checksum_ctx_create(svn_checksum_md5, pool);
> b->checksum_finalized = FALSE;
> b->md5_checksum = svn_checksum_dup(rep->md5_checksum, pool);
> - b->len = rep->expanded_size ? rep->expanded_size : rep->size;
> + b->len = rep->expanded_size;
> b->off = 0;
> b->fulltext_cache_key = fulltext_cache_key;
> b->pool = svn_pool_create(pool);
> b->filehandle_pool = svn_pool_create(pool);
>
> + SVN_ERR(build_rep_list(&b->rs_list, &b->base_window,
> + &b->src_state, &b->len, fs, rep,
> + b->filehandle_pool));
> +
> if (SVN_IS_VALID_REVNUM(fulltext_cache_key.revision))
> b->current_fulltext = svn_stringbuf_create_ensure
> ((apr_size_t)b->len,
> @@ -4645,10 +4667,6 @@ rep_read_get_baton(struct rep_read_baton
> else
> b->current_fulltext = NULL;
>
> - SVN_ERR(build_rep_list(&b->rs_list, &b->base_window,
> - &b->src_state, fs, rep,
> - b->filehandle_pool));
> -
> /* Save our output baton. */
> *rb_p = b;
>
>
>
Received on 2012-10-17 02:02:38 CEST

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