On 2024-05-14 13:07, Andrew Cooper wrote:
On 14/05/2024 9:13 am, Leigh Brown wrote:
Although using integer comparison to compare doubles kind of
works, it's annoying to see domains slightly out of order when
sorting by cpu%.
Add a compare_dbl() function and update compare_cpu_pct() to
call it.
Signed-off-by: Leigh Brown <le...@solinno.co.uk>
---
tools/xentop/xentop.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/tools/xentop/xentop.c b/tools/xentop/xentop.c
index 545bd5e96d..99199caec9 100644
--- a/tools/xentop/xentop.c
+++ b/tools/xentop/xentop.c
@@ -85,6 +85,7 @@ static void set_delay(const char *value);
static void set_prompt(const char *new_prompt, void (*func)(const
char *));
static int handle_key(int);
static int compare(unsigned long long, unsigned long long);
+static int compare_dbl(double, double);
static int compare_domains(xenstat_domain **, xenstat_domain **);
static unsigned long long tot_net_bytes( xenstat_domain *, int);
static bool tot_vbd_reqs(xenstat_domain *, int, unsigned long long
*);
@@ -422,6 +423,16 @@ static int compare(unsigned long long i1,
unsigned long long i2)
return 0;
}
+/* Compares two double precision numbers, returning -1,0,1 for <,=,>
*/
+static int compare_dbl(double d1, double d2)
+{
+ if(d1 < d2)
+ return -1;
+ if(d1 > d2)
+ return 1;
+ return 0;
+}
+
/* Comparison function for use with qsort. Compares two domains
using the
* current sort field. */
static int compare_domains(xenstat_domain **domain1, xenstat_domain
**domain2)
@@ -523,7 +534,7 @@ static double get_cpu_pct(xenstat_domain *domain)
static int compare_cpu_pct(xenstat_domain *domain1, xenstat_domain
*domain2)
{
- return -compare(get_cpu_pct(domain1), get_cpu_pct(domain2));
+ return -compare_dbl(get_cpu_pct(domain1), get_cpu_pct(domain2));
Oh, we were doing an implicit double->unsigned long long conversion.
Over the range 0.0 to 100.0, that ought to work as expected. What kind
of out-of-order are you seeing?
Nevertheless, this should comparison should clearly be done using
doubles. AFACT, get_cpu_pct() shouldn't ever return a NaN, so I think
this simple form is fine.
Oleksii: This is another bugfix to xentop, and should be considered for
4.19 at this point.
~Andrew
Perhaps I overthought it, and this approach might be better:
--- a/tools/xentop/xentop.c
+++ b/tools/xentop/xentop.c
@@ -523,7 +523,8 @@ static double get_cpu_pct(xenstat_domain *domain)
static int compare_cpu_pct(xenstat_domain *domain1, xenstat_domain
*domain2)
{
- return -compare(get_cpu_pct(domain1), get_cpu_pct(domain2));
+ return -compare(get_cpu_pct(domain1) * 100.0,
+ get_cpu_pct(domain2) * 100.0);
}
/* Prints cpu percentage statistic */
