131 lines
5.0 KiB
Diff
131 lines
5.0 KiB
Diff
From 9d324aabba1e20b6f3ed8a673d03f2c8bc0ad8d8 Mon Sep 17 00:00:00 2001
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From: Alon Levy <alevy@redhat.com>
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Date: Tue, 22 Mar 2011 12:27:59 +0200
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Subject: [PATCH] spice-qemu-char.c: add throttling
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BZ: 672191
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upstream: not submitted (explained below)
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Adds throttling support to spicevmc chardev. Uses a timer to avoid recursing:
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1. spice-server: reds.c: read_from_vdi_port
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2. qemu: spice-qemu-char.c: vmc_read
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3. chr_write_unblocked
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(calls virtio_serial_throttle_port(port, false))
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4. qemu: virtio ...
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5. qemu: spice-qemu-char.c: spice_chr_write
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6. qemu: spice-qemu-char.c: wakeup (calls into spice-server)
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7. spice-server: ...
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8. qemu: spice-qemu-char.c: vmc_read
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Instead, in vmc_read if we were throttled and we are just about to return
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all the bytes we will set a timer to be triggered immediately to call
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chr_write_unblocked. Then we return after 2 above, and 3 is called from the
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timer callback. This also means we can later remove some ugly recursion protection
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from spice-server.
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The other tricky point in this patch is not returning the leftover chunk twice.
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When we throttle, by definition we have data that spice server didn't consume.
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It is being kept by virtio-serial, and by us. The next vmc_read callback needs
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to not return it, but just do unthrottling. Then virtio will give us the remaining
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chunk as usual in spice_chr_write, and we will pass it to spice server in the
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next vmc_read.
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This patch relies on Amit's series to expose throttling to chardev's, which
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was not accepted upstream, and will not be accepted upstream until the mainloop
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is reworked to use glib.
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---
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spice-qemu-char.c | 39 +++++++++++++++++++++++++++++++++++----
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1 file changed, 35 insertions(+), 4 deletions(-)
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diff --git a/spice-qemu-char.c b/spice-qemu-char.c
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index 7e8eaa9..eeeb32e 100644
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--- a/spice-qemu-char.c
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+++ b/spice-qemu-char.c
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@@ -1,4 +1,6 @@
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#include "config-host.h"
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+#include "qemu-common.h"
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+#include "qemu-timer.h"
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#include "trace.h"
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#include "ui/qemu-spice.h"
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#include <spice.h>
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@@ -25,6 +27,7 @@ typedef struct SpiceCharDriver {
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uint8_t *datapos;
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ssize_t bufsize, datalen;
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uint32_t debug;
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+ QEMUTimer *unblock_timer;
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} SpiceCharDriver;
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static int vmc_write(SpiceCharDeviceInstance *sin, const uint8_t *buf, int len)
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@@ -50,6 +53,17 @@ static int vmc_write(SpiceCharDeviceInstance *sin, const uint8_t *buf, int len)
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return out;
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}
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+static void spice_chr_unblock(void *opaque)
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+{
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+ SpiceCharDriver *scd = opaque;
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+
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+ if (scd->chr->chr_write_unblocked == NULL) {
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+ dprintf(scd, 1, "%s: backend doesn't support unthrottling.\n", __func__);
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+ return;
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+ }
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+ scd->chr->chr_write_unblocked(scd->chr->handler_opaque);
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+}
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+
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static int vmc_read(SpiceCharDeviceInstance *sin, uint8_t *buf, int len)
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{
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SpiceCharDriver *scd = container_of(sin, SpiceCharDriver, sin);
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@@ -61,9 +75,16 @@ static int vmc_read(SpiceCharDeviceInstance *sin, uint8_t *buf, int len)
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scd->datapos += bytes;
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scd->datalen -= bytes;
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assert(scd->datalen >= 0);
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- if (scd->datalen == 0) {
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- scd->datapos = 0;
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- }
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+ }
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+ if (scd->datalen == 0 && scd->chr->write_blocked) {
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+ dprintf(scd, 1, "%s: unthrottling (%d)\n", __func__, bytes);
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+ scd->chr->write_blocked = false;
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+ /*
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+ * set a timer instead of calling scd->chr->chr_write_unblocked directly,
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+ * because that will call back into spice_chr_write (see
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+ * virtio-console.c:chr_write_unblocked), which is unwanted.
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+ */
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+ qemu_mod_timer(scd->unblock_timer, 0);
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}
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trace_spice_vmc_read(bytes, len);
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return bytes;
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@@ -135,6 +156,7 @@ static void vmc_unregister_interface(SpiceCharDriver *scd)
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static int spice_chr_write(CharDriverState *chr, const uint8_t *buf, int len)
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{
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SpiceCharDriver *s = chr->opaque;
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+ int read_bytes;
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dprintf(s, 2, "%s: %d\n", __func__, len);
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vmc_register_interface(s);
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@@ -147,7 +169,15 @@ static int spice_chr_write(CharDriverState *chr, const uint8_t *buf, int len)
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s->datapos = s->buffer;
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s->datalen = len;
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spice_server_char_device_wakeup(&s->sin);
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- return len;
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+ read_bytes = len - s->datalen;
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+ if (read_bytes != len) {
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+ dprintf(s, 1, "%s: throttling: %d < %d (%zd)\n", __func__,
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+ read_bytes, len, s->bufsize);
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+ s->chr->write_blocked = true;
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+ /* We'll get passed in the unconsumed data with the next call */
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+ s->datalen = 0;
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+ }
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+ return read_bytes;
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}
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static void spice_chr_close(struct CharDriverState *chr)
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@@ -225,6 +255,7 @@ int qemu_chr_open_spice(QemuOpts *opts, CharDriverState **_chr)
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chr->chr_close = spice_chr_close;
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chr->chr_guest_open = spice_chr_guest_open;
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chr->chr_guest_close = spice_chr_guest_close;
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+ s->unblock_timer = qemu_new_timer_ms(vm_clock, spice_chr_unblock, s);
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#if SPICE_SERVER_VERSION < 0x000901
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/* See comment in vmc_state() */
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