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From "Jean-Jacques Clar" <JJC...@novell.com>
Subject APR and Apache Time Format Questions
Date Mon, 03 Mar 2003 19:03:22 GMT
I have two Questions/Suggestions to improve the current performance 
of Apache 2.
 
1: 
Apache and Apr are keeping the time stamp in uSEC, it implies multiple

calls to apr_time_sec(), which is just doing a 64 bits division to
transform 
uSEC in sec. 
I think this is a waste of CPU cycles for nothing.
 
What about creating a new define called: 
 
#define APR_HAS_USEC.
 
The else of that option could allow apache to run using ONLY sec for
all 
apr_time_t field removing all 64 bits division to transform uSEC to
sec.
The size of the apr_time_t variables could also be changed to 32 bits
and 
calls to gettimeofday() changed to time() in that configuration.
 
Why is apache using uSEC? 
Time variables are mostly used in seconds at run-time, and http 
requirements use seconds.
 
The performance gain is minor but measurable: between 1 and 2.5% on 
my box (from 1 to 4 CPUs).
 
-----------

 
Questions: 
2-
If one does not fly, it should also be valuable to change the return
format 
of apr_date_parse_http() to be in seconds instead of uSEC.
This is a snippet of the last part of that function:
 
--- boc ---
    /* ap_mplode_time uses tm_usec and tm_gmtoff fields, but they
haven't 
     * been set yet. 
     * It should be safe to just zero out these values.
     * tm_usec is the number of microseconds into the second.  HTTP
only
     * cares about second granularity.
     * tm_gmtoff is the number of seconds off of GMT the time is.  By
     * definition all times going through this function are in GMT, so
this
     * is zero. 
     */
    ds.tm_usec = 0;
--- eoc ---
 
and then the time is exploded to match the apr_time_t format.
 
A call to apr_date_parse_httpd() is usually followed by a call to
apr_time_sec(), 
which do a 64 bits division to get the time in second.
What about having a new function called apr_date_parse_httpd_sec(),
which 
skip the end part of apr_time_exp_get() and return seconds?
It implies a small change to apr_time_exp_get() and moving the core
code in 
apr_time_exp_get() to apr_time_exp_get_sec().:
 
--- boc ---
APR_DECLARE(apr_status_t) apr_time_exp_get(apr_time_t *t,
apr_time_exp_t *xt)
{
    apr_status_t ret;
 
    ret = apr_time_exp_get_sec(t, xt);
    if (ret == APR_SUCCESS)
        *t = *t * APR_USEC_PER_SEC + xt->tm_usec;
 
    return ret;
}
--- eoc ---
 
Thank you,
 
Jean-Jacques 


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