[mp2 filters] allocating modperl_wbucket_t or not

Currently we allocate a wbucket of type modperl_wbucket_t for each
filter invocation. If it's not a streaming filter (i.e. manipulates
bucket brigades or doesn't use read/print) it's never going to need
wbucket. wbucket consumes 16404 bytes, the filter struct without
wbucket consumes 60 bytes. In order not to penalize non-streaming
filters, I suggest not to allocate wbucket if and not until it's first
used.

So we save a lot of wasteful memory allocations if streaming API is
not used (allocating 60 bytes instead of 16464). If the streaming API
is used we pay with if(!wb) conditional for each
$f->print and $f->flush calls, since there is no special entry point
for streaming filters (a filter can be anything).

Here is the patch. Notice that you have to rebuild from scratch if you
test it, since sources under xs/ have a broken dependency on header
files under src/, therefore they won't see the change in the size of
modperl_filter_t and you will get all kind of weird segfaults (I spent
quite some time trying to understand what's going on until it hit me
and I'd rebuilt from scratch).


Index: src/modules/perl/modperl_filter.c
===================================================================
RCS file: /home/cvs/modperl-2.0/src/modules/perl/modperl_filter.c,v
retrieving revision 1.77
diff -u -r1.77 modperl_filter.c
--- src/modules/perl/modperl_filter.c   11 Dec 2003 07:38:41 -0000      1.77
+++ src/modules/perl/modperl_filter.c   11 Dec 2003 09:20:45 -0000
@@ -20,6 +20,19 @@

 #define MP_FILTER_POOL(f) f->r ? f->r->pool : f->c->pool

+/* allocate wbucket memory using malloc and not request pools, since
+ * we may need many of these if the filter is invoked multiple
+ * times */
+#define WBUCKET_INIT(wb, p, next_filter)                   \
+    if (!wb) {                                             \
+        wb = (modperl_wbucket_t *)safemalloc(sizeof(*wb)); \
+        wb->pool    = p;                                   \
+        wb->filters = &next_filter;                        \
+        wb->outcnt  = 0;                                   \
+        wb->r       = NULL;                                \
+        wb->header_parse = 0;                              \
+    }
+
 /* this function is for tracing only, it's not optimized for performance */
 static int is_modperl_filter(ap_filter_t *f)
 {
@@ -264,9 +277,7 @@
     filter->mode = mode;
     filter->f = f;
     filter->pool = p;
-    filter->wbucket.pool = p;
-    filter->wbucket.filters = &f->next;
-    filter->wbucket.outcnt = 0;
+    filter->wbucket = NULL;

     if (mode == MP_INPUT_FILTER_MODE) {
         filter->bb_in  = NULL;
@@ -739,7 +750,8 @@
         filter->flush = 0;
     }

-    filter->rc = modperl_wbucket_flush(&filter->wbucket, add_flush_bucket);
+    WBUCKET_INIT(filter->wbucket, filter->pool, filter->f->next);
+    filter->rc = modperl_wbucket_flush(filter->wbucket, add_flush_bucket);
     if (filter->rc != APR_SUCCESS) {
         return filter->rc;
     }
@@ -779,7 +791,8 @@
                                                    const char *buf,
                                                    apr_size_t *len)
 {
-    return modperl_wbucket_write(aTHX_ &filter->wbucket, buf, len);
+    WBUCKET_INIT(filter->wbucket, filter->pool, filter->f->next);
+    return modperl_wbucket_write(aTHX_ filter->wbucket, buf, len);
 }

 apr_status_t modperl_output_filter_handler(ap_filter_t *f,
Index: src/modules/perl/modperl_types.h
===================================================================
RCS file: /home/cvs/modperl-2.0/src/modules/perl/modperl_types.h,v
retrieving revision 1.69
diff -u -r1.69 modperl_types.h
--- src/modules/perl/modperl_types.h    19 Aug 2003 05:01:22 -0000      1.69
+++ src/modules/perl/modperl_types.h    11 Dec 2003 09:20:46 -0000
@@ -193,7 +193,7 @@
     ap_filter_t *f;
     char *leftover;
     apr_ssize_t remaining;
-    modperl_wbucket_t wbucket;
+    modperl_wbucket_t *wbucket;
     apr_bucket *bucket;
     apr_bucket_brigade *bb_in;
     apr_bucket_brigade *bb_out;


__________________________________________________________________
Stas Bekman            JAm_pH ------> Just Another mod_perl Hacker
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