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Date: Wed, 05 Nov 2014 11:53:23 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v3 2/2] main-loop: Use epoll on Linux
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To: Fam Zheng <famz@redhat.com>, qemu-devel@nongnu.org
Cc: kwolf@redhat.com, Stefan Hajnoczi <stefanha@redhat.com>



On 27/10/2014 08:30, Fam Zheng wrote:
> 
> +static int epoll_prepare(int epollfd,
> +                         GPollFD *fds, guint nfds,
> +                         GPollFD **g_poll_fds,
> +                         guint *g_poll_nfds,
> +                         int **g_poll_fd_idx)

Please pass the QEMUPollContext to epoll_prepare.

> +        if (ctx->last_fds) {
> +            close(ctx->epollfd);
> +        }
> +        ctx->epollfd = epoll_create(1);

Please use epoll_create1 with the EPOLL_CLOEXEC flag.

> +        if (ctx->epollfd < 0) {
> +            perror("epoll_create");
> +            abort();
> +        }

Interesting.  Is it cheaper to do this than to compute a symmetric
difference?

I am worried that the epoll_create fails with EMFILE, and that the
destruction/recreation happens often with networking (which uses
qemu_set_fd_handler2) if you use the right workload.

Paolo