nntp: reduce memory overhead of zlib

[public-inbox.git] / lib / PublicInbox / NNTPdeflate.pm

diff --git a/lib/PublicInbox/NNTPdeflate.pm b/lib/PublicInbox/NNTPdeflate.pm
index 66210bfa84c040c1a2caa90f8d4c01e59d2e5c67..78da2a588674fe59b48ab1793ab1b2cfbc9dc576 100644 (file)
--- a/lib/PublicInbox/NNTPdeflate.pm
+++ b/lib/PublicInbox/NNTPdeflate.pm
@@ -2,13 +2,18 @@
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 
 # RFC 8054 NNTP COMPRESS DEFLATE implementation
-# Warning, enabling compression for C10K NNTP clients is rather
-# expensive in terms of memory use.
 #
 # RSS usage for 10K idle-but-did-something NNTP clients on 64-bit:
-#   TLS + DEFLATE :  1.8 GB  (MemLevel=9, 1.2 GB with MemLevel=8)
-#   TLS only      :  <200MB
-#   plain         :   <50MB
+#   TLS + DEFLATE[a] :  1.8 GB  (MemLevel=9, 1.2 GB with MemLevel=8)
+#   TLS + DEFLATE[b] :  ~300MB
+#   TLS only         :  <200MB
+#   plain            :   <50MB
+#
+# [a] - initial implementation using per-client Deflate contexts and buffer
+#
+# [b] - memory-optimized implementation using a global deflate context.
+#       It's less efficient in terms of compression, but way more
+#       efficient in terms of server memory usage.
 package PublicInbox::NNTPdeflate;
 use strict;
 use warnings;
@@ -23,11 +28,11 @@ my %IN_OPT = (
        -AppendOutput => 1,
 );
 
-my %OUT_OPT = (
+# global deflate context and buffer
+my $zbuf = \(my $buf = '');
+my $zout = Compress::Raw::Zlib::Deflate->new(
        # nnrpd (INN) and Compress::Raw::Zlib favor MemLevel=9,
-       # but the zlib C library and git use MemLevel=8
-       # as the default.  Using 8 drops our memory use with 10K
-       # TLS clients from 1.8 GB to 1.2 GB, but...
+       # but the zlib C library and git use MemLevel=8 as the default.
        # FIXME: sometimes clients fail with 8, so we use 9
        # -MemLevel => 9,
 
@@ -43,7 +48,6 @@ sub enable {
        unlock_hash(%$self);
        bless $self, $class;
        $self->{zin} = [ Compress::Raw::Zlib::Inflate->new(%IN_OPT), '' ];
-       $self->{zout} = [ Compress::Raw::Zlib::Deflate->new(%OUT_OPT), '' ];
 }
 
 # overrides PublicInbox::NNTP::compressed
@@ -74,31 +78,42 @@ sub do_read ($$$$) {
 # override PublicInbox::DS::msg_more
 sub msg_more ($$) {
        my $self = $_[0];
-       my $zout = $self->{zout};
 
        # $_[1] may be a reference or not for ->deflate
-       my $err = $zout->[0]->deflate($_[1], $zout->[1]);
+       my $err = $zout->deflate($_[1], $zbuf);
        $err == Z_OK or die "->deflate failed $err";
        1;
 }
 
-# SUPER is PublicInbox::DS::write, so $_[1] may be a reference or not
+sub zflush ($) {
+       my ($self) = @_;
+
+       my $deflated = $zbuf;
+       $zbuf = \(my $next = '');
+
+       my $err = $zout->flush($deflated, Z_FULL_FLUSH);
+       $err == Z_OK or die "->flush failed $err";
+
+       # We can still let the lower socket layer do buffering:
+       PublicInbox::DS::msg_more($self, $$deflated);
+}
+
+# compatible with PublicInbox::DS::write, so $_[1] may be a reference or not
 sub write ($$) {
        my $self = $_[0];
-       return $self->SUPER::write($_[1]) if ref($_[1]) eq 'CODE';
-       my $zout = $self->{zout};
-       my $deflated = pop @$zout;
+       return PublicInbox::DS::write($self, $_[1]) if ref($_[1]) eq 'CODE';
+
+       my $deflated = $zbuf;
+       $zbuf = \(my $next = '');
 
        # $_[1] may be a reference or not for ->deflate
-       my $err = $zout->[0]->deflate($_[1], $deflated);
+       my $err = $zout->deflate($_[1], $deflated);
        $err == Z_OK or die "->deflate failed $err";
-       $err = $zout->[0]->flush($deflated, Z_PARTIAL_FLUSH);
+       $err = $zout->flush($deflated, Z_FULL_FLUSH);
        $err == Z_OK or die "->flush failed $err";
 
-       # PublicInbox::DS::write puts partial writes into another buffer,
-       # so we can prepare the next deflate buffer:
-       $zout->[1] = '';
-       $self->SUPER::write(\$deflated);
+       # We can still let the socket layer do buffering:
+       PublicInbox::DS::write($self, $deflated);
 }
 
 1;