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In general, the new NIF-based file routines are faster than the old
efile driver.
However, on some computers, building the entire OTP system is somewhat
slower. It turns out that it is because 'erlc' cheated by turning off
the IO thread pool (using '+A0') to avoid context switches between
scheduler threads and threads in the IO thread pool. The new file
routines perform IO on dirty IO threads, and there is (by intent) no
way to force the operations to occur on scheduler threads to avoid
the context switches
What we can do to is to use a small (4Kb) read-ahead buffer for files
opened for reading (only) in list mode (which is how the compiler
opens its input files). The buffering reduces the number of context
switches between scheduler threads and dirty IO threads. On my
computer that seems to slightly speed up building of the entire OTP
system.
The buffer should do no harm. The only potential for harm I can
think of is random access to a file opened in read mode, where
the read-ahead buffer could slightly decrease performance. That
does not seems to be a likely use case in practice, though.
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This improves the latency of file operations as dirty schedulers
are a bit more eager to run jobs than async threads, and use a
single global queue rather than per-thread queues, eliminating the
risk of a job stalling behind a long-running job on the same thread
while other async threads sit idle.
There's no such thing as a free lunch though; the lowered latency
comes at the cost of increased busy-waiting which may have an
adverse effect on some applications. This behavior can be tweaked
with the +sbwt flag, but unfortunately it affects all types of
schedulers and not just dirty ones. We plan to add type-specific
flags at a later stage.
sendfile has been moved to inet_drv to lessen the effect of a nasty
race; the cooperation between inet_drv and efile has never been
airtight and the socket dying at the wrong time (Regardless of
reason) could result in fd aliasing. Moving it to the inet driver
makes it impossible to trigger this by closing the socket in the
middle of a sendfile operation, while still allowing it to be
aborted -- something that can't be done if it stays in the file
driver.
The race still occurs if the controlling process dies in the short
window between dispatching the sendfile operation and the dup(2)
call in the driver, but it's much less likely to happen now.
A proper fix is in the works.
--
Notable functional differences:
* The use_threads option for file:sendfile/5 no longer has any
effect.
* The file-specific DTrace probes have been removed. The same
effect can be achieved with normal tracing together with the
nif__entry/nif__return probes to track scheduling.
--
OTP-14256
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* maint:
Update HOWTO with wxWidgets build examples
https should be mapped to url and not seealso
Update kernel appup for OTP-20.2
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* siri/appups-20.2:
Update kernel appup for OTP-20.2
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d8d07a7593d811 that added the to_dis option to the compiler no longer
works when merged to master. That is because of 79f28cfd8df1b7
that removed some unused code in erts_debug.
Fix this by adding a new function erts_debug:dis_to_file/2 and
use it from compile module where we have access to the filename
(in beam_listing we only have an opened file).
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Conflicts:
lib/compiler/src/beam_listing.erl
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and drop _id suffix.
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to make sure it's kept alive.
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as a preparation for async auto-connect requests.
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and remove ugly encoding fallback as {fun, ...}
DFLAGS_NEW_FUN_TAGS has been supported by vm/erl_interface/jinterface
since R13 or even older.
Renamed test case obsolete_funs to term2bin_tuple_fallbacks
and removed test for {fun,...} fallback
and added missing test for bitstring fallback {Binary, Bits}.
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* maint:
stdlib: Make ets:i/1 exit cleaner upon ^D (old Erlang shell)
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* hasse/stdlib/fix_ets_i_1/OTP-14663:
stdlib: Make ets:i/1 exit cleaner upon ^D (old Erlang shell)
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* dgud/kernel/get_chars_raw_echo_off:
Let io:get_chars/2 (echo off) fetch chars without eol
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* rickard/null-chars/ERL-370/OTP-14543:
Don't allow null chars in various strings
Conflicts:
erts/emulator/beam/erl_alloc.types
erts/preloaded/ebin/erlang.beam
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* maint:
Revert "Merge branch 'rickard/null-char-filenames/ERL-370/OTP-14543' into maint"
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This reverts commit 0717a2194e863f3a78595184ccc5637697f03353, reversing
changes made to 71a40658a0cef8b3e25df3a8e48a72d0563a89bf.
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Various places that now reject null chars inside strings
- Primitive file operations reject it in filenames.
- Primitive environment variable operations reject it in
names and values.
- os:cmd() reject it in its input.
Also '=' characters are rejected by primitive environment
variable operations in environment variable names.
Documentation has been updated to document null characters
in these types of data as invalid. Currently these operations
accept null chars at the end of strings, but that will change
in the future.
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Instead of crashing, ^D now exits Erlang if started with -oldshell.
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* maint:
Don't allow null in filenames
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The test case erts_debug_SUITE:df/1 in the emulator test suite is
about 4 times faster with this change.
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* maint:
erts, stdlib: Fix xmllint warning
Update runtime deps to depend on new stdlib functionality
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OTP-13133
Fixed dns lookup in case of server close connection with econnrefused
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~tw and new string functions are new since OTP-20 (stdlib-3.4)
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* siri/string-new-api: (28 commits)
hipe (test): Do not use deprecated functions in string(3)
dialyzer (test): Do not use deprecated functions in string(3)
eunit (test): Do not use deprecated functions in string(3)
system (test): Do not use deprecated functions in string(3)
system (test): Do not use deprecated functions in string(3)
mnesia (test): Do not use deprecated functions in string(3)
Deprecate old string functions
observer: Do not use deprecated functions in string(3)
common_test: Do not use deprecated functions in string(3)
eldap: Do not use deprecated functions in string(3)
et: Do not use deprecated functions in string(3)
os_mon: Do not use deprecated functions in string(3)
debugger: Do not use deprecated functions in string(3)
runtime_tools: Do not use deprecated functions in string(3)
asn1: Do not use deprecated functions in string(3)
compiler: Do not use deprecated functions in string(3)
sasl: Do not use deprecated functions in string(3)
reltool: Do not use deprecated functions in string(3)
kernel: Do not use deprecated functions in string(3)
hipe: Do not use deprecated functions in string(3)
...
Conflicts:
lib/eunit/src/eunit_lib.erl
lib/observer/src/crashdump_viewer.erl
lib/reltool/src/reltool_target.erl
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error_logger implements a simple handler which is used when no other
handler is active. This handler is used during system startup, when
there is no guarantee that all modules are loaded and must therefore
not use any other modules for the formatting.
Commit 41b856a2cb270ef807beaa84afe1bb890de5f237 introduced a call to
io_lib:printable_list/1, which is now removed.
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If printable range is set to 'unicode', the simple error logger will now
recognize code points > 255 and print lists containing these as strings.
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When option 'echo off' is set no line editing is done and
there is no need to wait until eol for io:get_chars.
This solves the issue of not needing to wait for eol until chars are
received from stdin, sometimes the user wants direct/raw unprocessed
input.
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* maint:
Always reply to sync requests
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Otherwise processes doing io could get stuck.
See ERL-472.
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Conflicts:
erts/emulator/beam/bif.c
erts/emulator/beam/dist.c
erts/emulator/beam/dist.h
erts/emulator/beam/erl_bif_info.c
erts/emulator/beam/erl_node_tables.c
erts/emulator/beam/erl_node_tables.h
erts/emulator/beam/external.c
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* maint-20:
Updated OTP version
Update release notes
Update version numbers
Fix doc for the 'quiet' option; it defaults to false
asn1: Fix missing quotes of external encoding call
Add a dedicated close function for TCP ports to prevent issues like ERL-430/448
Close TCP ports properly on send timeout
erts: Add missing release note
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* john/kernel/fix-disk-log-docs/OTP-14498:
Fix doc for the 'quiet' option; it defaults to false
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* raimo/kernel/fix-spec-for-inet-get_rc-0/ERL-454:
Improve spec and doc for inet:get_rc/0
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* siri/appups-21:
Update sasl/test/test_lib.hrl with recent versions of kernel and stdlib
Update appups in kernel, stdlib, and sasl for OTP-21.0
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