On Sun, 2002-09-29 at 17:19, Greg Stein wrote: > On Sun, Sep 29, 2002 at 01:05:38AM -0000, [EMAIL PROTECTED] wrote: > > brianp 2002/09/28 18:05:38 > > > > Modified: buckets apr_brigade.c > > Log: > > Rewrite of apr_brigade_writev(). It's now more efficient for > > both large and small inputs: zero-copy for data larger than 8KB, > > fewer operations (and fewer branches) per for-loop iteration > > for the <= 8KB case. > > Cool! > > I presume you found the "count the length up front" to have no impact in the > short case? Thus, going ahead and doing the count and then the switch to > transient buckets?
Right, counting the length up front added some overhead, but it also eliminated the need for a lot of conditional and arithmetic operations per iteration of the main copy loop, so the change basically paid for itself. > One thing I just realized, though: if there is no flush function, then a > transient could be a problem. I just double-checked apr_brigade_write() and > it switches over to HEAP buckets for that case. Should _writev follow the > same pattern? You mean, in case the caller then deletes the underlying storage for the strings in the iovec? Yes, in that case we should use heap buckets. I'll make a change for this. Both the _writev and the _write functions really need a warning in the documentation: "not guaranteed to be zero copy, so build your own buckets if you're trying to pass very large amounts of data." Brian
