Re: [Qemu-devel] [RFC PATCH 19/21] plugins: add an example hotblocks plugin

["Pavel Dovgalyuk" <dovgaluk@ispras.ru>]

I guess this one is too tcg-dependent.
It count TB's, but breaking code into TBs may depend on many things,
like breakpoints, record/replay, ...

I mean that this measuring approach may be used only in some specific
cases, and not ok as an example.

Pavel Dovgalyuk

> -----Original Message-----
> From: Alex Bennée [mailto:alex.bennee@linaro.org]
> Sent: Friday, October 05, 2018 6:49 PM
> To: qemu-devel@nongnu.org
> Cc: Pavel.Dovgaluk@ispras.ru; vilanova@ac.upc.edu; cota@braap.org; Alex Bennée; Stefan
> Hajnoczi
> Subject: [RFC PATCH 19/21] plugins: add an example hotblocks plugin
> 
> This plugin attempts to track hotblocks by total execution count and
> average time to return to block. It is intended to be lower impact
> than saving a long log file and post-processing it.
> 
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> ---
>  trace/plugins/hotblocks/hotblocks.c | 69 +++++++++++++++++++++++++++++
>  1 file changed, 69 insertions(+)
>  create mode 100644 trace/plugins/hotblocks/hotblocks.c
> 
> diff --git a/trace/plugins/hotblocks/hotblocks.c b/trace/plugins/hotblocks/hotblocks.c
> new file mode 100644
> index 0000000000..e9166ad1a5
> --- /dev/null
> +++ b/trace/plugins/hotblocks/hotblocks.c
> @@ -0,0 +1,69 @@
> +/*
> + * Execution Hotblocks Plugin
> + *
> + * Copyright (c) 2018
> + * Written by Alex Bennée <alex.bennee@linaro.org>
> + *
> + * This code is licensed under the GNU GPL v2.
> + */
> +
> +#include <stdint.h>
> +#include <stdio.h>
> +#include <glib.h>
> +#include <time.h>
> +#include "plugins.h"
> +
> +/* Plugins need to take care of their own locking */
> +GMutex lock;
> +GHashTable *hotblocks;
> +
> +typedef struct {
> +    uintptr_t pc;
> +    unsigned int hits;
> +    struct timespec last;
> +    unsigned long total_time;
> +} ExecCount;
> +
> +bool plugin_init(const char *args)
> +{
> +    hotblocks = g_hash_table_new(NULL, g_direct_equal);
> +    return true;
> +}
> +
> +char *plugin_status(void)
> +{
> +    GString *report = g_string_new("We have ");
> +    char *r;
> +    g_mutex_lock(&lock);
> +    g_string_append_printf(report, "%ud entries in the hash table\n",
> +                           g_hash_table_size(hotblocks));
> +    g_mutex_unlock(&lock);
> +    r = report->str;
> +    g_string_free(report, FALSE);
> +    return r;
> +}
> +
> +bool exec_tb(void *tb, uintptr_t pc)
> +{
> +    ExecCount *cnt;
> +    struct timespec current;
> +    clock_gettime(CLOCK_MONOTONIC, &current);
> +
> +    g_mutex_lock(&lock);
> +    cnt = (ExecCount *) g_hash_table_lookup(hotblocks, (gconstpointer) pc);
> +    if (cnt) {
> +        cnt->hits++;
> +        cnt->total_time += current.tv_nsec - cnt->last.tv_nsec;
> +        cnt->last = current;
> +    } else {
> +        cnt = g_new0(ExecCount, 1);
> +        cnt->pc = pc;
> +        cnt->last = current;
> +        cnt->hits = 1;
> +        g_hash_table_insert(hotblocks, (gpointer) pc, (gpointer) cnt);
> +    }
> +    g_mutex_unlock(&lock);
> +
> +    /* As we are collecting up samples no reason to continue tracing */
> +    return false;
> +}
> --
> 2.17.1