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From Torsten Foertsch <>
Subject about removing the last hash lookup in the interp management code
Date Wed, 14 Nov 2007 16:34:48 GMT
Hi Philippe,

in the threading branch this line and the corresponding get in 
modperl_interp_pool_select() are the last occurrences of hash lookups in the 
interp management.

      (void)apr_pool_userdata_set((void *)r, "MODPERL_R", NULL, r->pool);

I am thinking of removing it. But it requires a extension to the request pool 
and changes to the httpd.

The idea is to introduce typed pools with extensions. Something like

int type = apr_pool_type_register(void);

int ext = apr_pool_extension_register(int type, size_t size);

apr_pool_t *pool = apr_pool_create_typed_pool(int type);

void *ptr = apr_pool_get_extension(apr_pool_t *pool, int ext);

A call to apr_pool_type_register adds an element to some internal 
apr_array_header_t and returns the index of the new element.

apr_pool_extension_register gets this index (or pool type) and increments said 
array element by "size" rounded up to a proper alignment and returns the 
value of the array element before the increment.

These 2 functions are to be called during initialization.

Then at runtime when a typed pool is needed pool structure is allocated plus 
at the end of the pool enough space to hold all extensions. To access a 
registered extension one calls apr_pool_get_extension which returns a pointer
to the amount of space registered during initialization.

In the httpd this would mean at init time:

extern int req_pool_type;
extern int conn_pool_type;
static int req_pool_type = apr_pool_type_register();
static int conn_pool_type = apr_pool_type_register();

Then the req pool creation is converted to

  req_pool = apr_pool_create_typed_pool( req_pool_type )

In mod_perl this could look like:


static my_req_pool_ext = apr_pool_extension_register(req_pool_type,


void *ptr = apr_pool_get_extension(pool, my_req_pool_ext);
*ptr = (void *)r;  /* instead of apr_pool_userdata_set */

I hope it is clear what I mean. I think not only mod_perl can benefit these 
pool extensions. Apache would have to export the main pool types like 
req_pool_type and conn_pool_type. Modules can add their own pool types.

Does that make sense? What are the odds on getting it into apr and apache?


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