On 2016-09-03 4:15 PM, Christian Heimes wrote:
On 2016-09-04 00:03, Yury Selivanov wrote:
On 2016-09-03 12:27 PM, Brett Cannon wrote:
Below is the `co_extra` section of PEP 523 with the update saying that
users are expected to put a tuple in the field for easier simultaneous
use of the field.
Since the `co_extra` discussions do not affect CPython itself I'm
planning on landing the changes stemming from the PEP probably on Monday.
Tuples are immutable. If you have multiple co_extra users then they
will have to either mutate tuple (which isn't always possible, for
instance, you can't increase size), or to replace it with another tuple.
Creating lists is a bit more expensive, but item access speed should be
in the same ballpark.
Another question -- sorry if this was discussed before -- why do we want
a PyObject* there at all? I.e. why don't we create a dedicated struct
CoExtraContainer to manage the stuff in co_extra? My understanding is
that the users of co_extra are C-level python optimizers and profilers,
which don't need the overhead of CPython API.
This way my work to add an extra caching layer (which I'm very much
willing to continue to work on) wouldn't require another set of extra
fields for code objects.
Quick idea before I go to bed:
You could adopt a similar API to OpenSSL's CRYPTO_get_ex_new_index()
API,
https://www.openssl.org/docs/manmaster/crypto/CRYPTO_get_ex_new_index.html
static int code_index = 0;
int PyCodeObject_NewIndex() {
return code_index++;
}
A library like Pyjion has to acquire an index first. In further calls it
uses the index as offset into the new co_extra field. Libraries don't
have to hard-code their offset and two libraries will never conflict.
PyCode_New() can pre-populate co_extra with a PyTuple of size
code_index. This avoids most resizes if you load Pyjion early. For
code_index == 0 leaf the field NULL.
Sounds like a very good idea!
Yury
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