Re: [patch 00/11] ANNOUNCE: "Syslets", generic asynchronous system call support


* Evgeniy Polyakov <johnpol@xxxxxxxxxxx> wrote:

[...] it still has a problem - syscall blocks and the same thread thus
is not allowed to continue execution and fill the pipe - so what if
system issues thousands of requests and there are only tens of working
thread at most. [...]

the same thread is allowed to continue execution even if the system call
blocks: take a look at async_schedule(). The blocked system-call is 'put
aside' (in a sleeping thread), the kernel switches the user-space
context (registers) to a free kernel thread and switches to it - and
returns to user-space as if nothing happened - allowing the user-space
context to 'fill the pipe' as much as it can. Or did i misunderstand
your point?

basically there's SYSLET_ASYNC for 'always async' and SYSLET_SYNC for
'always sync' - but the default syslet behavior is: 'try sync and switch
transparently to async on demand'. The testcode i sent very much uses
this. (and this mechanism is in essence Zach's fibril-switching thing,
but done via kernel threads.)

Ingo
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