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36
is that we get a curl_multi_timeout() that should also work with old-style
39
37
applications that use curl_multi_perform().
41
The easy handle argument was removed fom the curl_multi_socket() function
42
because having it there would require the application to do a socket to easy
43
handle conversion on its own. I find it very unlikely that applications
44
would want to do that and since libcurl would need such a lookup on its own
45
anyway since we didn't want to force applications to do that translation
46
code (it would be optional), it seemed like an unnecessary option.
39
We also added a timer callback that makes libcurl call the application when
40
the timeout value changes, and you set that with curl_multi_setopt().
48
Instead I created an internal "socket to easy handles" hash table that given
42
We created an internal "socket to easy handles" hash table that given
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43
a socket (file descriptor) return the easy handle that waits for action on
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44
that socket. This hash is made using the already existing hash code
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45
(previously only used for the DNS cache).
53
To make libcurl be able to report plain sockets in the socket callback, I
54
had to re-organize the internals of the curl_multi_fdset() etc so that the
47
To make libcurl able to report plain sockets in the socket callback, we had
48
to re-organize the internals of the curl_multi_fdset() etc so that the
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49
conversion from sockets to fd_sets for that function is only done in the
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50
last step before the data is returned. I also had to extend c-ares to get a
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51
function that can return plain sockets, as that library too returned only
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52
fd_sets and that is no longer good enough. The changes done to c-ares have
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53
been committed and are available in the c-ares CVS repository destined to be
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included in the upcoming c-ares 1.3.1 release.
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The 'shiper' tool is the test application I wrote that uses the new
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curl_multi_socket() in its current state. It seems to be working and it uses
64
the API as it is documented and supposed to work. It is still using
65
select(), because I needed that during development (like until I had the
66
socket hash implemented etc) and because I haven't yet learned how to use
69
The hiper/shiper tools are very simple and initiates lots of connections and
70
have them running for the test period and then kills them all.
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Since I wasn't done with the implementation until early January I haven't
73
had time to run very many measurements and checks, but I have done a few
74
runs with up to a few hundred connections (with a single active one). The
75
curl_multi_socket() invoke then takes 3-6 microseconds in average (using the
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read-only-1-byte-at-a-time hack). If this number does increase a lot when we
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add connections, it certainly matches my in my opinion very ambitious goal.
78
We are now below the 60 microseconds "per socket action" goal. It is
79
destined to be somewhat higher the more connections we have since the hash
80
table gets more populated and the splay tree will grow etc.
82
Some tests at 7000 and 9000 connections showed that the socket hash lookup
83
is somewhat of a bottle neck. Its current implementation may be a bit too
84
limiting. It simply has a fixed-size array, and on each entry in the array
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it has a linked list with entries. So the hash only checks which list to
86
scan through. The code I had used so for used a list with merely 7 slots (as
87
that is what the DNS hash uses) but with 7000 connections that would make an
88
average of 1000 nodes in each list to run through. I upped that to 97 slots
89
(I believe a prime is suitable) and noticed a significant speed increase. I
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need to reconsider the hash implementation or use a rather large default
91
value like this. At 9000 connections I was still below 10us per call.
54
included in the c-ares 1.3.1 release.
56
We have done a test runs with up to 9000 connections (with a single active
57
one). The curl_multi_socket() invoke then takes less than 10 microseconds in
58
average (using the read-only-1-byte-at-a-time hack). We are now below the
59
60 microseconds "per socket action" goal (the extra 50 is the time libevent
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The curl_multi_socket() API is implemented according to how it is
65
documented. We deem it ready to use.
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http://curl.haxx.se/libcurl/c/curl_multi_socket.html
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68
http://curl.haxx.se/libcurl/c/curl_multi_timeout.html
added
removed
lib/README.multi_socket
