[erlang-patches] Pollset per scheduler and bind port to scheduler

Wei Cao <>
Wed Jul 11 04:21:02 CEST 2012

I added a macro to conditional compile the patch because I think it
can be more selectable, I can remove the macro, fix the compilation
error and test on mingw platform in later version.

how about provide another BIF named port_flag (like process_flag) to
let user bind port to a given scheduler?



Wei Cao

> Message: 1
> Date: Mon, 9 Jul 2012 15:05:02 +0200
> From: Lukas Larsson <>
> To: 
> Subject: Re: [erlang-patches] Pollset per scheduler and bind port to
>         scheduler
> Message-ID: <>
> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed
> Hi,
> Thanks a lot for these patches!
> Multiple poll-sets is something which we have been thinking about doing
> for a while now, but haven't as yet gotten around to do. So it is great
> that you have taken the time to implement it!
> What is the reason for not enabling the multiple poll-set functionality
> by default? Have you seen any scenarios where it is unwanted? Or
> platforms which the approach does not work?
> When compiling the multiple poll-set patch on Windows we got an error[1]
> because the compiler we use there does not allow empty structs. Do you
> have a windows environment available to test your patch on? For
> instructions on how to set up a test environment on windows see[2]. We
> really want this patch, but have to make sure that it works properly on
> all platforms as it is a core change to how erts handler fd polling.
> When the Windows compile issue is fixed, we will include this patch in
> our daily builds and let you know of any test failures which we find.
> Regarding binding a port to a scheduler, we are unsure about building
> more functionality on top of the internal `scheduler` option as it
> effects the soft-realtime properties of the system. Generally we do not
> want to add functionality which exposes the internal scheduler semantics
> to the programmer, but rather make the scheduler more intelligent about
> where they schedule tasks. We'll have to discuss internally what we want
> to do with this.
> Thanks!
> Lukas
> [1]: Windows 7, mingw, vs 10 compiler
> cc.sh   -O3 -I/c/jenkins/workspace/compile-master-opu-win32/erts/win32   -D_WIN32_WINNT=0x0500 -DWINVER=0x0500 -DERTS_MIXED_MSYS_VC -DSTATIC_ERLANG_DRIVER  -DHAVE_CONFIG_H  -DUSE_THREADS -DWIN32_THREADS  -Iwin32/opt/plain -Ibeam -Isys/win32 -Isys/common -Iwin32 -Izlib  -Ipcre -Ihipe -I../include -I../include/win32 -I../include/internal -I../include/internal/win32 -c sys/common/erl_check_io.c -o obj/win32/opt/plain/erl_check_io.o
> sys/common/erl_check_io.c(99) : error C2016: C requires that a struct or union has at least one member
> [2]: http://www.erlang.org/doc/installation_guide/INSTALL-WIN32.html
> On 09/07/12 08:47, Wei Cao wrote:
>> In our proxy project which has massive network IO, we found
>> erts_check_io()  become system bottleneck,
>> a call to erts_check_io() would take 500 microseconds to complete, and
>> invoked about 3.5k times per second
>> under heavy preesure, which resulted in the average response time of
>> user request longer than 2 milliseconds,
>> so that limited system throughput down, while cpus were idle(in
>> starvation) at the same time.
>> This patch allocates one pollset for each scheduler, so that each
>> scheduler could invoke erts_check_io()
>> on its own pollset concurrently. To be incorporate well with port
>> migration, all used fd in each port're recorded,
>> removed from old scheduler's pollset and added to new scheduler's when
>> port is migrating between schedulers.
>> After applying this patch, together with binding process&port with
>> schedulers, erts_check_io() is invoked about 230k
>> times per second (dozens of times more than before), and throughtput
>> increases from 45k to 105k, so it works.
>> This patch SHOULD be compiled with ./configure
>> Pollset per scheduler:
>> git fetch git://github.com/weicao/otp.git pollset_per_scheduler
>> https://github.com/weicao/otp/compare/weicao:master...weicao:pollset_per_scheduler
>> https://github.com/weicao/otp/compare/weicao:master...weicao:pollset_per_scheduler.patch
>> Bind port to scheduler:
>> git fetch git://github.com/weicao/otp.git bind_port_to_scheduler
>> https://github.com/weicao/otp/compare/weicao:pollset_per_scheduler...weicao:bind_port_to_scheduler
>> https://github.com/weicao/otp/compare/weicao:pollset_per_scheduler...weicao:bind_port_to_scheduler.patch
>> --
>> Best,
>> Wei Cao
>> _______________________________________________
>> erlang-patches mailing list
>> http://erlang.org/mailman/listinfo/erlang-patches

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