On 14/05/2024 1:36 pm, Leigh Brown wrote:
> Hello,
>
> 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?
>
> Without patch:
>
> xentop - 13:29:01 Xen 4.18.2
> 13 domains: 1 running, 12 blocked, 0 paused, 0 crashed, 0 dying, 0 shutdown
> Mem: 67030640k total, 33097800k used, 33932840k free CPUs: 24 @ 3693MHz
> NAME STATE CPU(sec) CPU(%) MEM(k) MEM(%) MAXMEM(k) MAXMEM(%)
> icecream --b--- 2597 6.6 4194368 6.3 4195328 6.3
> xendd --b--- 4016 5.4 524268 0.8 525312 0.8
> Domain-0 -----r 1059 1.7 1048576 1.6 1048576 1.6
> neon --b--- 826 1.1 2097216 3.1 2098176 3.1
> blender --b--- 121 0.2 1048640 1.6 1049600 1.6
> bread --b--- 69 0.1 524352 0.8 525312 0.8
> bob --b--- 502 0.3 16777284 25.0 16778240 25.0
> cheese --b--- 225 0.5 1048384 1.6 1049600 1.6
> cassini --b--- 489 0.4 3145792 4.7 3146752 4.7
> chickpea --b--- 67 0.1 524352 0.8 525312 0.8
> lentil --b--- 67 0.1 262208 0.4 263168 0.4
> fusilli --b--- 159 0.2 524352 0.8 525312 0.8
> pizza --b--- 359 0.5 524352 0.8 525312 0.8
>
> With patch:
>
> xentop - 13:30:17 Xen 4.18.2
> 13 domains: 1 running, 12 blocked, 0 paused, 0 crashed, 0 dying, 0 shutdown
> Mem: 67030640k total, 33097788k used, 33932852k free CPUs: 24 @ 3693MHz
> NAME STATE CPU(sec) CPU(%) MEM(k) MEM(%) MAXMEM(k) MAXMEM(%)
> xendd --b--- 4020 5.7 524268 0.8 525312 0.8
> icecream --b--- 2600 3.8 4194368 6.3 4195328 6.3
> Domain-0 -----r 1060 1.5 1048576 1.6 1048576 1.6
> neon --b--- 827 1.1 2097216 3.1 2098176 3.1
> cheese --b--- 225 0.7 1048384 1.6 1049600 1.6
> pizza --b--- 359 0.5 524352 0.8 525312 0.8
> cassini --b--- 490 0.4 3145792 4.7 3146752 4.7
> fusilli --b--- 159 0.2 524352 0.8 525312 0.8
> bob --b--- 502 0.2 16777284 25.0 16778240 25.0
> blender --b--- 121 0.2 1048640 1.6 1049600 1.6
> bread --b--- 69 0.1 524352 0.8 525312 0.8
> chickpea --b--- 67 0.1 524352 0.8 525312 0.8
> lentil --b--- 67 0.1 262208 0.4 263168 0.4
Ah, so it's the rounding, and a straight cast discards the fractional part.
I think your patch is fine, although it could do with a mention of why
this goes wrong in the commit message. I'm happy to adjust on commit.
~Andrew
