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Since the removal of pseudo-hash support in Perl 5.10, the
"fields" module no longer provides the space or speed benefits
it did in 5.8. It also does not allow for compile-time checks,
only run-time checks.
To me, the extra developer overhead in maintaining "use fields"
args has become a hassle. None of our non-DS-related code uses
fields.pm, nor do any of our current dependencies. In fact,
Danga::Socket (which DS was originally forked from) and its
subclasses are the only fields.pm users I've ever encountered in
the wild. Removing fields may make our code more approachable
to other Perl hackers.
So stop using fields.pm and locked hashes, but continue to
document what fields do for non-trivial classes.
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This matches PublicInbox::IMAP::event_step and will allow us to
handle blob retrievals from git asynchronously without falling
over on pipelined requests.
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It must be a scalar reference, unlike ->write
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I didn't wait until September to do it, this year!
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We don't need to keep an empty buffer around in the common case
when a client is sending us completely inflatable requests and
we're able to read them in one go.
This only seems to save about 2M with 10K NNTPS clients using
COMPRESS, so it's not a huge win, but better than nothing.
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We won't need further layering after enabling compression. So
be explicit about which sub we're calling when we hit ->do_read
from NNTP and eliminate the need for the comment.
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Add some checks for errors at initialization, though there's not
much that can be done with ENOMEM-type errors aside from
dropping clients.
We can also get rid of the scary FIXME for MemLevel=8. It was a
stupid error on my part in the original per-client deflate
stream implementation calling C::R::Z::{Inflate,Deflate} in
array context and getting the extra dualvar error code as a
string result, causing the {zin}/{zout} array refs to have
extra array elements.
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Using Z_FULL_FLUSH at the right places in our event loop, it
appears we can share a single zlib deflate context across ALL
clients in a process.
The zlib deflate context is the biggest factor in per-client
memory use, so being able to share that across many clients
results in a large memory savings.
With 10K idle-but-did-something NNTP clients connected to a
single process on a 64-bit system, TLS+DEFLATE used around
1.8 GB of RSS before this change. It now uses around 300 MB.
TLS via IO::Socket::SSL alone uses <200MB in the same situation,
so the actual memory reduction is over 10x.
This makes compression less efficient and bandwidth increases
around 45% in informal testing, but it's far better than no
compression at all. It's likely around the same level of
compression gzip gives on the HTTP side.
Security implications with TLS? I don't know, but I don't
really care, either... public-inbox-nntpd doesn't support
authentication and it's up to the client to enable compression.
It's not too different than Varnish caching gzipped responses
on the HTTP side and having responses go to multiple HTTPS
clients.
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This is only tested so far with my patches to Net::NNTP at:
https://rt.cpan.org/Ticket/Display.html?id=129967
Memory use in C10K situations is disappointing, but that's
the nature of compression.
gzip compression over HTTPS does have the advantage of not
keeping zlib streams open when clients are idle, at the
cost of worse compression.
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