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From Hyrum K Wright <hy...@hyrumwright.org>
Subject Re: svn commit: r1104160 - /subversion/trunk/subversion/libsvn_subr/utf.c
Date Tue, 17 May 2011 12:16:23 GMT
apr_atomic_xchgptr() and friends are not available on APR 0.9.  (This
is causing a buildbot build failure.)

-Hyrum

On Tue, May 17, 2011 at 11:27 AM,  <stefan2@apache.org> wrote:
> Author: stefan2
> Date: Tue May 17 11:27:25 2011
> New Revision: 1104160
>
> URL: http://svn.apache.org/viewvc?rev=1104160&view=rev
> Log:
> Speed up UTF8 conversion, especially if APR_HAS_THREADS.
> Provide global
>
> * subversion/libsvn_subr/utf.c
>  (SVN_UTF_NTOU_XLATE_HANDLE, SVN_UTF_UTON_XLATE_HANDLE):
>   make them identifiable by address
>  (xlat_ntou_static_handle, xlat_uton_static_handle):
>   introduce global translation map pointers as 1st level cache
>  (get_xlate_handle_node): match standard xlat types by address;
>   try global map pointers first before falling back to the hash
>  (put_xlate_handle_node): match standard xlat types by address;
>   push old global maps to hash
>
> Modified:
>    subversion/trunk/subversion/libsvn_subr/utf.c
>
> Modified: subversion/trunk/subversion/libsvn_subr/utf.c
> URL: http://svn.apache.org/viewvc/subversion/trunk/subversion/libsvn_subr/utf.c?rev=1104160&r1=1104159&r2=1104160&view=diff
> ==============================================================================
> --- subversion/trunk/subversion/libsvn_subr/utf.c (original)
> +++ subversion/trunk/subversion/libsvn_subr/utf.c Tue May 17 11:27:25 2011
> @@ -29,6 +29,7 @@
>  #include <apr_strings.h>
>  #include <apr_lib.h>
>  #include <apr_xlate.h>
> +#include <apr_atomic.h>
>
>  #include "svn_string.h"
>  #include "svn_error.h"
> @@ -42,9 +43,13 @@
>
>
>
> -#define SVN_UTF_NTOU_XLATE_HANDLE "svn-utf-ntou-xlate-handle"
> -#define SVN_UTF_UTON_XLATE_HANDLE "svn-utf-uton-xlate-handle"
> -#define SVN_APR_UTF8_CHARSET "UTF-8"
> +/* Use these static strings to maximize performance on standard conversions.
> + * Any strings on other locations are still valid, however.
> + */
> +static const char *SVN_UTF_NTOU_XLATE_HANDLE = "svn-utf-ntou-xlate-handle";
> +static const char *SVN_UTF_UTON_XLATE_HANDLE = "svn-utf-uton-xlate-handle";
> +
> +static const char *SVN_APR_UTF8_CHARSET = "UTF-8";
>
>  #if APR_HAS_THREADS
>  static apr_thread_mutex_t *xlate_handle_mutex = NULL;
> @@ -79,6 +84,13 @@ typedef struct xlate_handle_node_t {
>    memory leak. */
>  static apr_hash_t *xlate_handle_hash = NULL;
>
> +/* "1st level cache" to standard conversion maps. We may access these
> + * using atomic xchange ops, i.e. without further thread synchronization.
> + * If the respective item is NULL, fallback to hash lookup.
> + */
> +static volatile void *xlat_ntou_static_handle = NULL;
> +static volatile void *xlat_uton_static_handle = NULL;
> +
>  /* Clean up the xlate handle cache. */
>  static apr_status_t
>  xlate_cleanup(void *arg)
> @@ -91,6 +103,10 @@ xlate_cleanup(void *arg)
>  #endif
>   xlate_handle_hash = NULL;
>
> +  /* ensure no stale objects get accessed */
> +  xlat_ntou_static_handle = NULL;
> +  xlat_uton_static_handle = NULL;
> +
>   return APR_SUCCESS;
>  }
>
> @@ -183,6 +199,19 @@ get_xlate_handle_node(xlate_handle_node_
>     {
>       if (xlate_handle_hash)
>         {
> +          /* 1st level: global, static items */
> +          if (userdata_key == SVN_UTF_NTOU_XLATE_HANDLE)
> +            old_node = apr_atomic_xchgptr(&xlat_ntou_static_handle, NULL);
> +          else if (userdata_key == SVN_UTF_UTON_XLATE_HANDLE)
> +            old_node = apr_atomic_xchgptr(&xlat_uton_static_handle, NULL);
> +
> +          if (old_node && old_node->valid)
> +            {
> +              *ret = old_node;
> +              return SVN_NO_ERROR;
> +            }
> +
> +          /* 2nd level: hash lookup */
>  #if APR_HAS_THREADS
>           apr_err = apr_thread_mutex_lock(xlate_handle_mutex);
>           if (apr_err != APR_SUCCESS)
> @@ -321,9 +350,20 @@ put_xlate_handle_node(xlate_handle_node_
>   assert(node->next == NULL);
>   if (!userdata_key)
>     return;
> +
> +  /* push previous global node to the hash */
>   if (xlate_handle_hash)
>     {
>       xlate_handle_node_t **node_p;
> +
> +      /* 1st level: global, static items */
> +      if (userdata_key == SVN_UTF_NTOU_XLATE_HANDLE)
> +        node = apr_atomic_xchgptr(&xlat_ntou_static_handle, node);
> +      else if (userdata_key == SVN_UTF_UTON_XLATE_HANDLE)
> +        node = apr_atomic_xchgptr(&xlat_uton_static_handle, node);
> +      if (node == NULL)
> +        return;
> +
>  #if APR_HAS_THREADS
>       if (apr_thread_mutex_lock(xlate_handle_mutex) != APR_SUCCESS)
>         SVN_ERR_MALFUNCTION_NO_RETURN();
>
>
>

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