From: Sasha Levin <levinsasha928@gmail.com>
To: Matthias Diener <matthias.diener@mdiener.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5] hashtable: introduce a small and naive hashtable
Date: Sun, 16 Sep 2012 13:30:26 +0200 [thread overview]
Message-ID: <5055B852.4010906@gmail.com> (raw)
In-Reply-To: <CAKBUcnA4b8HaV3-20C8QXXgFXW4ZDfOc6SvYCFsA3mtdyEd89Q@mail.gmail.com>
[-- Attachment #1: Type: text/plain, Size: 1746 bytes --]
On 09/16/2012 01:08 AM, Matthias Diener wrote:
> Sasha Levin (levinsasha928 <at> gmail.com) wrote:
>> On Sat, Sep 15, 2012 at 5:14 PM, Mathieu Desnoyers
>> <mathieu.desnoyers <at> efficios.com> wrote:
>>> * Sasha Levin (levinsasha928 <at> gmail.com) wrote:
> [...]
>>>> +#define hash_init(hashtable) \
>>>> +({ \
>>>> + int __i; \
>>>> + \
>>>> + for (__i = 0; __i < HASH_BITS(hashtable); __i++) \
>>>
>>> I think this fails to initialize the whole table. You'd need
>>>
>>> HASH_BITS -> HASH_SIZE
>>
>> Right.
>>
>> Unfortunately it's pretty hard catching something like this :/
>>
>>> Which brings the following question: how did you test this code ? It
>>> would be nice to have a small test module along with this patchset that
>>> stress-tests this simple hash table in various configurations (on stack,
>>> in data, etc).
>>
>> I do two things:
>>
>> - A small userspace test (since this header works just fine from
>> userspace as well).
>
>
> It would be interesting to run some experiments with this hashtable in
> userspace.
> Could you post the test code here?
Sure, I've attached the test code. There are 2 things to remember it:
1. The code looks like crap :) I've never intended it to be seen by others.
2. It should be used in the context of "sanitized" kernel headers so it could
be included directly. I usually work in the directory of lkvm, and compile this
code using:
gcc -Iinclude/ -I../../include/ -O0 -ggdb hashtest.c
[-- Attachment #2: hashtest.c --]
[-- Type: text/x-csrc, Size: 1352 bytes --]
#define BITS_PER_LONG 64
#include <linux/kernel.h>
#include <linux/hashtable.h>
#include <kvm/util.h>
#include <linux/log2.h>
#include <assert.h>
struct my_data {
int x;
struct hlist_node node;
};
static DECLARE_HASHTABLE(test, 10);
static struct my_data *values[1000000];
struct my_data *get_data(int v)
{
struct my_data *p;
struct hlist_node *n;
hash_for_each_possible(test, p, n, node, v)
if (p->x == v)
return p;
return NULL;
}
bool verify(int i)
{
if (values[i] == NULL && get_data(i))
printf("No data, but found at %p (%d)\n", get_data(i), i);
if (values[i])
return get_data(i) ? true : false;
else
return get_data(i) ? false : true;
}
int main(void)
{
int i;
hash_init(test);
printf("Empty? %d\n", hash_empty(test));
while (1) {
for (i = 0; i < ARRAY_SIZE(values); i++) {
int r = rand() % 3;
if (i % 10000 == 0) {
printf("\r%d ...", i);
fflush(stdout);
}
switch (r) {
case 0:
assert(verify(i));
if (values[i])
break;
values[i] = malloc(sizeof(values[i]));
values[i]->x = i;
hash_add(test, &values[i]->node, i);
assert(verify(i));
break;
case 1:
assert(verify(i));
break;
case 2:
assert(verify(i));
if (values[i]) {
hash_del(&values[i]->node);
free(values[i]);
values[i] = NULL;
}
assert(verify(i));
break;
}
}
}
return 0;
}
next prev parent reply other threads:[~2012-09-16 11:30 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-15 23:08 [PATCH v5] hashtable: introduce a small and naive hashtable Matthias Diener
2012-09-16 11:30 ` Sasha Levin [this message]
-- strict thread matches above, loose matches on Subject: below --
2012-09-15 9:53 Sasha Levin
2012-09-15 15:14 ` Mathieu Desnoyers
2012-09-15 15:47 ` Sasha Levin
2012-09-16 19:33 ` Mathieu Desnoyers
2012-09-16 19:48 ` Sasha Levin
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