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Re: [PATCH 7/7] aio-posix: remove idle poll handlers to improve scalabil
From: |
Stefan Hajnoczi |
Subject: |
Re: [PATCH 7/7] aio-posix: remove idle poll handlers to improve scalability |
Date: |
Mon, 9 Mar 2020 16:37:07 +0000 |
On Fri, Mar 06, 2020 at 03:17:40PM +0100, Paolo Bonzini wrote:
> On 06/03/20 14:50, Stefan Hajnoczi wrote:
> >> Not sure I understand the "almost" part. If it's accessed only from
> >> aio_poll() it is protected via either AIO_WAIT_WHILE or the BQL, not by
> >> ctx->list_lock; if it's protected by ctx->list_lock (using
> >> qemu_lockcnt_inc in readers), it is an RCU list.
> > aio_remove_fd_handler() removes nodes from the list during
> > aio_set_fd_handler(), but only while holding ctx->list_lock and the
> > count is zero (no readers).
> >
> > All other access is done from with ctx->list_lock incremented. This
> > code needs to be reentrant in case of nested aio_poll() but nothing else
> > will access the list at the same time.
>
> Oh, I see, adds are only done under ctx->list_lock and those are the
> part that need the write barriers in the RCU iterators.
I'll update the comment when merging this series.
Stefan
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- Re: [PATCH 2/7] aio-posix: move RCU_READ_LOCK() into run_poll_handlers(), (continued)
- [PATCH 6/7] aio-posix: support userspace polling of fd monitoring, Stefan Hajnoczi, 2020/03/05
- [PATCH 4/7] aio-posix: simplify FDMonOps->update() prototype, Stefan Hajnoczi, 2020/03/05
- [PATCH 3/7] aio-posix: extract ppoll(2) and epoll(7) fd monitoring, Stefan Hajnoczi, 2020/03/05
- [PATCH 5/7] aio-posix: add io_uring fd monitoring implementation, Stefan Hajnoczi, 2020/03/05
- [PATCH 7/7] aio-posix: remove idle poll handlers to improve scalability, Stefan Hajnoczi, 2020/03/05
Re: [PATCH 0/7] aio-posix: polling scalability improvements, Stefan Hajnoczi, 2020/03/09