Chris Brannon <[email protected]> wrote: > Eric Wong <[email protected]> writes: > > > Do you know which pipes are which? "lsof -p $PID +E" can help > > with connectivity checking, as can script/dtas-graph in > > https://80x24.org/dtas.git if you have Graph::Easy > > Yes. I'm attaching my lsof output and a typescript. > > The processes of interest here are 4849 public-inbox-convert and 4879 > git cat-file. > PID 4849's FD 11 is the write end of a pipe, with 4879's stdin as the > read end. > PID 4849's FD 12 is the read end of a pipe, with 4879's stdout as the > write end. At the point of the hang, 4849 is trying to write a SHA1 to > FD 11, while 4879 is writing an email message to its stdout.
OK. That is strange, because the current values are sized conservatively for Linux (which has larger-than-required PIPE_BUF size). > > Some shots in the dark: > > > > 2. Tweak $PIPE_BUFSIZ and/or MAX_INFLIGHT to smaller values. e.g. > > > > diff --git a/lib/PublicInbox/Git.pm b/lib/PublicInbox/Git.pm > > index 882a9a4a..ec40edd7 100644 > > --- a/lib/PublicInbox/Git.pm > > +++ b/lib/PublicInbox/Git.pm > > @@ -23,13 +23,12 @@ use Carp qw(croak carp); > > use Digest::SHA (); > > use PublicInbox::DS qw(dwaitpid); > > our @EXPORT_OK = qw(git_unquote git_quote); > > -our $PIPE_BUFSIZ = 65536; # Linux default > > +our $PIPE_BUFSIZ = 4096; # Linux default > > our $in_cleanup; > > our $RDTIMEO = 60_000; # milliseconds > > our $async_warn; # true in read-only daemons > > > > -use constant MAX_INFLIGHT => (POSIX::PIPE_BUF * 3) / > > - 65; # SHA-256 hex size + "\n" in preparation for git using non-SHA1 > > +use constant MAX_INFLIGHT => 4; > > This right here seems to have fixed it, when testing locally. Are you able to isolate whether $PIPE_BUFSIZ or MAX_INFLIGHT on it's own fixes it? And can you confirm the ->blocking(0) change had no effect on it's own? Capping MAX_INFLIGHT to a smaller value is probably fine (maybe 10 can work). The old MAX_INFLIGHT value ((512 * 3)/65 = 23) is actually extremely conservative for Linux, since the smallest possible PIPE_BUF is 4096 (so (4096 * 3)/65 = 189), but giant values don't help (and hurt interruptibility). However, making $PIPE_BUFSIZ smaller would increase syscalls made and hurt performance on systems with expensive syscalls. So I want to keep $PIPE_BUFSIZ as big as reasonable. Setting `$PIPE_BUFSIZ = 1024 ** 2' ought to work on a system with giant pipes, even; but the default Linux pipe size is 65536 unless it's low on memory. I'm honestly at a loss on how to explain what went wrong for you because the existing values are OS-independent. I also do wonder if you've hit a kernel bug under low memory conditions. I've certainly encountered problems with TCP traffic hanging processes due to memory compaction. > PS. Thank you for that lsof command. I've never used lsof in that way; > I'll have to add that to my *nix debugging toolbelt. np :>
