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Re: [Qemu-devel] [PATCH] slirp: Signal free input buffer space to io-thr
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH] slirp: Signal free input buffer space to io-thread |
Date: |
Fri, 30 Mar 2012 20:37:29 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:10.0.1) Gecko/20120216 Thunderbird/10.0.1 |
Il 30/03/2012 19:43, Jan Kiszka ha scritto:
> This massively accelerates slirp reception speed: If data arrives
> faster than the guest can read it from the input buffer, the file
> descriptor for the corresponding socket was taken out of the fdset for
> select. However, the event of the guest reading enough data from the
> buffer was not signaled. Thus, the io-thread only noticed this change
> on the next time-driven poll. Fix this by kicking the io-thread as
> required.
>
> Signed-off-by: Jan Kiszka <address@hidden>
> ---
>
> Hell, this was really annoying when working with slirp, specifically
> with KVM irqchip enabled (as it reduces userspace exits). But I never
> really found the time to dig deep enough. And now it turned out to be
> so simple! http://thread.gmane.org/gmane.comp.emulators.qemu/141975 was
> the key for me.
>
> slirp/sbuf.c | 6 ++++++
> 1 files changed, 6 insertions(+), 0 deletions(-)
>
> diff --git a/slirp/sbuf.c b/slirp/sbuf.c
> index 5a1ccbf..637f8fe 100644
> --- a/slirp/sbuf.c
> +++ b/slirp/sbuf.c
> @@ -6,6 +6,7 @@
> */
>
> #include <slirp.h>
> +#include <main-loop.h>
>
> static void sbappendsb(struct sbuf *sb, struct mbuf *m);
>
> @@ -18,6 +19,8 @@ sbfree(struct sbuf *sb)
> void
> sbdrop(struct sbuf *sb, int num)
> {
> + int limit = sb->sb_datalen / 2;
> +
> /*
> * We can only drop how much we have
> * This should never succeed
> @@ -29,6 +32,9 @@ sbdrop(struct sbuf *sb, int num)
> if(sb->sb_rptr >= sb->sb_data + sb->sb_datalen)
> sb->sb_rptr -= sb->sb_datalen;
>
> + if (sb->sb_cc < limit && sb->sb_cc + num >= limit) {
> + qemu_notify_event();
> + }
> }
>
> void
Looks good!
Paolo