Ryan did this a while back, and couldn't get it fast enough for small writes (might need some reference here)
Simply put - the overhead of abstraction wasn't worth it. A lot of people using template engines are practically doing response.writeHead(200, ...); response.end(template.compile()) which doesn't need the writev fluff. Tim On 23 April 2013 14:15, Mikeal Rogers <[email protected]> wrote: > Is there a reason not to just have the underlying libuv *always* writev when > it has more than one pending buffer to write? > > I'm wondering whey we can't just optimize this behind the scenes, is there a > reason we need to map each stream write a write syscall? > > -Mikeal > > On Apr 22, 2013, at 5:01PM, Isaac Schlueter <[email protected]> wrote: > >> There's a syscall called `writev` that lets you write an array (ie, >> "Vector") of buffers of data rather than a single buffer. >> >> I'd like to support something like this for Streams in Node, mostly >> because it will allow us to save a lot of TCP write() calls, without >> having to copy data around, especially for chunked encoding writes. >> (We write a lot of tiny buffers for HTTP, it's kind of a nightmare, >> actually.) >> >> Fedor Indutny has already done basically all of the legwork to >> implement this. Where we're stuck is the API surface, and here are >> some options. Node is not a democracy, but your vote counts anyway, >> especially if it's a really good vote with some really good argument >> behind it :) >> >> Goals: >> 1. Make http more good. >> 2. Don't break existing streams. >> 3. Don't make things hard. >> 4. Don't be un-node-ish >> >> For all of these, batched writes will only be available if the >> Writable stream implements a `_writev()` method. No _writev, no >> batched writes. Any bulk writes will just be passed to _write(chunk, >> encoding, callback) one at a time in the order received. >> >> In all cases, any queued writes will be passed to _writev if that >> function is implemented, even if they're just backed up from a slow >> connection. >> >> >> Ideas: >> >> >> A) stream.bulk(function() { stream.write('hello'); >> stream.write('world'); stream.end('!\n') }) >> >> Any writes done in the function passed to `stream.bulk()` will be >> batched into a single writev. >> >> Upside: >> - Easier to not fuck up and stay frozen forever. There is basically >> zero chance that you'll leave the stream in a corked state. (Same >> reason why domain.run() is better than enter()/exit().) >> >> Downsides: >> - easier to fuck up and not actually batch things. eg, >> s.bulk(function(){setTimeout(...)}) >> - bulk is a weird name. "batch" maybe? Nothing else really seems >> appropriate either. >> - somewhat inflexible, since all writes have to be done in the same >> function call >> >> >> B) stream.cork(); stream.write('hello'); stream.write('world'); >> stream.end('!\n'); stream.uncork(); >> >> Any writes done while corked will be flushed to _writev() when uncorked. >> >> Upside: >> - Easy to implement >> - Strictly more flexible than stream.bulk(writer). (Can trivially >> implement a bulk function using cork/uncork) >> - Useful for cases outside of writev (like corking a http request >> until the connection is established) >> >> Downsides: >> - Easy to fuck up and stay corked forever. >> - Two functions instead of just one (double the surface area increase) >> >> >> C) stream.writev([chunks,...], [encodings,...], callback) >> >> That is, implement a first-class top-level function called writev() >> which you can call with an array of chunks and an array of encodings. >> >> Upside: >> - No unnecessary surface area increase >> - NOW IT'S YOUR PROBLEM, NOT MINE, HAHA! (Seriously, though, it's >> less magical, simpler stream.Writable implementation, etc.) >> >> Downside: >> - A little bit tricky when you don't already have a list of chunks to >> send. (For example, with cork, you could write a bunch of stuff into >> it, and then uncork all at the end, and do one writev, even if it took >> a few ms to get it all.) >> - parallel arrays, ew. >> >> >> D) stream.writev([ {chunk:buf, encoding: blerg}, ...], callback) >> >> That is, same as C, but with an array of {chunk,encoding} objects >> instead of the parallel arrays. >> >> Same +/- as C, except the parallel array bit. This is probably how >> we'd call the implementation's stream._writev() anyway, so it'd be a >> bit simpler. >> >> >> >> Which of these seems like it makes the most sense to you? >> >> Is there another approach that you'd like to see here? (Note: "save >> all writes until end of tick always" and "copy into one big buffer" >> approaches are not feasible for obvious performance reasons.) >> >> -- >> -- >> Job Board: http://jobs.nodejs.org/ >> Posting guidelines: >> https://github.com/joyent/node/wiki/Mailing-List-Posting-Guidelines >> You received this message because you are subscribed to the Google >> Groups "nodejs" group. >> To post to this group, send email to [email protected] >> To unsubscribe from this group, send email to >> [email protected] >> For more options, visit this group at >> http://groups.google.com/group/nodejs?hl=en?hl=en >> >> --- >> You received this message because you are subscribed to the Google Groups >> "nodejs" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> For more options, visit https://groups.google.com/groups/opt_out. >> >> > > -- > -- > Job Board: http://jobs.nodejs.org/ > Posting guidelines: > https://github.com/joyent/node/wiki/Mailing-List-Posting-Guidelines > You received this message because you are subscribed to the Google > Groups "nodejs" group. > To post to this group, send email to [email protected] > To unsubscribe from this group, send email to > [email protected] > For more options, visit this group at > http://groups.google.com/group/nodejs?hl=en?hl=en > > --- > You received this message because you are subscribed to the Google Groups > "nodejs" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/groups/opt_out. > > -- -- Job Board: http://jobs.nodejs.org/ Posting guidelines: https://github.com/joyent/node/wiki/Mailing-List-Posting-Guidelines You received this message because you are subscribed to the Google Groups "nodejs" group. 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