53b56ca781
Changes to other patches are all just metadata/context changes except
for pvebackup_co_prepare() needing to call bdrv_co_unref() rather than
bdrv_unref(), because it is a coroutine itself. This is documented in
d6ee2e324e ("block-coroutine-wrapper: Introduce no_co_wrapper"). The
change is necessary, because one of the stable fixes converts
bdrv_unref and blk_unref into no_co_wrappers (in preparation for a
second patch to fix a hang with the block resize QMP command).
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
107 lines
4.9 KiB
Diff
107 lines
4.9 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Mon, 1 May 2023 13:34:43 -0400
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Subject: [PATCH] block: compile out assert_bdrv_graph_readable() by default
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reader_count() is a performance bottleneck because the global
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aio_context_list_lock mutex causes thread contention. Put this debugging
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assertion behind a new ./configure --enable-debug-graph-lock option and
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disable it by default.
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The --enable-debug-graph-lock option is also enabled by the more general
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--enable-debug option.
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(picked up from https://lists.nongnu.org/archive/html/qemu-devel/2023-05/msg00058.html)
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Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
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---
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block/graph-lock.c | 3 +++
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configure | 1 +
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meson.build | 2 ++
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meson_options.txt | 2 ++
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scripts/meson-buildoptions.sh | 4 ++++
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5 files changed, 12 insertions(+)
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diff --git a/block/graph-lock.c b/block/graph-lock.c
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index 454c31e691..259a7a0bde 100644
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--- a/block/graph-lock.c
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+++ b/block/graph-lock.c
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@@ -265,7 +265,10 @@ void bdrv_graph_rdunlock_main_loop(void)
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void assert_bdrv_graph_readable(void)
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{
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+ /* reader_count() is slow due to aio_context_list_lock lock contention */
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+#ifdef CONFIG_DEBUG_GRAPH_LOCK
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assert(qemu_in_main_thread() || reader_count());
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+#endif
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}
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void assert_bdrv_graph_writable(void)
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diff --git a/configure b/configure
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index 800b5850f4..a62a3e6be9 100755
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--- a/configure
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+++ b/configure
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@@ -806,6 +806,7 @@ for opt do
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--enable-debug)
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# Enable debugging options that aren't excessively noisy
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debug_tcg="yes"
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+ meson_option_parse --enable-debug-graph-lock ""
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meson_option_parse --enable-debug-mutex ""
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meson_option_add -Doptimization=0
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fortify_source="no"
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diff --git a/meson.build b/meson.build
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index c44d05a13f..d964e741e7 100644
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--- a/meson.build
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+++ b/meson.build
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@@ -1956,6 +1956,7 @@ if get_option('debug_stack_usage') and have_coroutine_pool
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have_coroutine_pool = false
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endif
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config_host_data.set10('CONFIG_COROUTINE_POOL', have_coroutine_pool)
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+config_host_data.set('CONFIG_DEBUG_GRAPH_LOCK', get_option('debug_graph_lock'))
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config_host_data.set('CONFIG_DEBUG_MUTEX', get_option('debug_mutex'))
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config_host_data.set('CONFIG_DEBUG_STACK_USAGE', get_option('debug_stack_usage'))
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config_host_data.set('CONFIG_GPROF', get_option('gprof'))
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@@ -3833,6 +3834,7 @@ summary_info += {'PIE': get_option('b_pie')}
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summary_info += {'static build': config_host.has_key('CONFIG_STATIC')}
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summary_info += {'malloc trim support': has_malloc_trim}
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summary_info += {'membarrier': have_membarrier}
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+summary_info += {'debug graph lock': get_option('debug_graph_lock')}
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summary_info += {'debug stack usage': get_option('debug_stack_usage')}
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summary_info += {'mutex debugging': get_option('debug_mutex')}
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summary_info += {'memory allocator': get_option('malloc')}
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diff --git a/meson_options.txt b/meson_options.txt
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index fc9447d267..bc857fe68b 100644
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--- a/meson_options.txt
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+++ b/meson_options.txt
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@@ -311,6 +311,8 @@ option('rng_none', type: 'boolean', value: false,
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description: 'dummy RNG, avoid using /dev/(u)random and getrandom()')
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option('coroutine_pool', type: 'boolean', value: true,
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description: 'coroutine freelist (better performance)')
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+option('debug_graph_lock', type: 'boolean', value: false,
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+ description: 'graph lock debugging support')
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option('debug_mutex', type: 'boolean', value: false,
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description: 'mutex debugging support')
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option('debug_stack_usage', type: 'boolean', value: false,
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diff --git a/scripts/meson-buildoptions.sh b/scripts/meson-buildoptions.sh
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index 009fab1515..30e1f25259 100644
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--- a/scripts/meson-buildoptions.sh
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+++ b/scripts/meson-buildoptions.sh
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@@ -21,6 +21,8 @@ meson_options_help() {
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printf "%s\n" ' QEMU'
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printf "%s\n" ' --enable-cfi Control-Flow Integrity (CFI)'
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printf "%s\n" ' --enable-cfi-debug Verbose errors in case of CFI violation'
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+ printf "%s\n" ' --enable-debug-graph-lock'
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+ printf "%s\n" ' graph lock debugging support'
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printf "%s\n" ' --enable-debug-mutex mutex debugging support'
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printf "%s\n" ' --enable-debug-stack-usage'
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printf "%s\n" ' measure coroutine stack usage'
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@@ -249,6 +251,8 @@ _meson_option_parse() {
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--datadir=*) quote_sh "-Ddatadir=$2" ;;
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--enable-dbus-display) printf "%s" -Ddbus_display=enabled ;;
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--disable-dbus-display) printf "%s" -Ddbus_display=disabled ;;
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+ --enable-debug-graph-lock) printf "%s" -Ddebug_graph_lock=true ;;
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+ --disable-debug-graph-lock) printf "%s" -Ddebug_graph_lock=false ;;
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--enable-debug-mutex) printf "%s" -Ddebug_mutex=true ;;
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--disable-debug-mutex) printf "%s" -Ddebug_mutex=false ;;
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--enable-debug-stack-usage) printf "%s" -Ddebug_stack_usage=true ;;
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