[dpdk-dev] replaced O(n^2) sort in sort_by_physaddr() with qsort() from standard library
Commit Message
Signed-off-by: Jay Rolette <rolette@infiniteio.com>
---
lib/librte_eal/linuxapp/eal/eal_memory.c | 59 +++++++++++---------------------
1 file changed, 20 insertions(+), 39 deletions(-)
Comments
Hi Jay,
Please read http://dpdk.org/dev#send for submission guidelines.
A description of why you do it would be welcome in the commit log.
> +static int
> +cmp_physaddr(const void *a, const void *b)
> +{
> +#ifndef RTE_ARCH_PPC_64
> + const struct hugepage_file *p1 = (const struct hugepage_file *)a;
> + const struct hugepage_file *p2 = (const struct hugepage_file *)b;
> +#else
> + // PowerPC needs memory sorted in reverse order from x86
Comments shall be C-style (/* */).
> + const struct hugepage_file *p1 = (const struct hugepage_file *)b;
> + const struct hugepage_file *p2 = (const struct hugepage_file *)a;
> +#endif
> + if (p1->physaddr < p2->physaddr)
> + return -1;
> + else if (p1->physaddr > p2->physaddr)
> + return 1;
> + else
> + return 0;
> +}
One of the goal of EAL is to avoid #ifdef.
So that function would probably be better located in
lib/librte_eal/common/include/arch/* with different implemenations
depending of the architecture.
Hi Thomas,
Please read http://dpdk.org/dev#send for submission guidelines.
>
I did when I was figuring out how to submit the patch, but possible I'm
missing something on the tools to get it to include the commit comment
correctly.
A description of why you do it would be welcome in the commit log.
>
How much are you looking for here? I thought replacing an O(n^2) algorithm
with qsort() was fairly self-evident. Less code and take advantage of
standard library code that is faster.
I get it in the general case. Just didn't seem necessary for this one.
> > +static int
> > +cmp_physaddr(const void *a, const void *b)
> > +{
> > +#ifndef RTE_ARCH_PPC_64
> > + const struct hugepage_file *p1 = (const struct hugepage_file *)a;
> > + const struct hugepage_file *p2 = (const struct hugepage_file *)b;
> > +#else
> > + // PowerPC needs memory sorted in reverse order from x86
>
> Comments shall be C-style (/* */).
>
Single line comments ('//') have been part of the C standard since C99. Is
DPDK following C89 or is this just a style thing? If it is a style thing, a
link to a page with the rubric would be helpful. I didn't see one on the
submission guidelines.
> > + const struct hugepage_file *p1 = (const struct hugepage_file *)b;
> > + const struct hugepage_file *p2 = (const struct hugepage_file *)a;
> > +#endif
> > + if (p1->physaddr < p2->physaddr)
> > + return -1;
> > + else if (p1->physaddr > p2->physaddr)
> > + return 1;
> > + else
> > + return 0;
> > +}
>
> One of the goal of EAL is to avoid #ifdef.
> So that function would probably be better located in
> lib/librte_eal/common/include/arch/* with different implemenations
> depending of the architecture.
>
Hmm... I was following the approach already used in the module. See
map_all_hugepages(), remap_all_hugepages().
Regards,
Jay
On Wed, Dec 17, 2014 at 09:07:45AM -0600, Jay Rolette wrote:
>
> > Comments shall be C-style (/* */).
> >
>
> Single line comments ('//') have been part of the C standard since C99. Is
> DPDK following C89 or is this just a style thing? If it is a style thing, a
> link to a page with the rubric would be helpful. I didn't see one on the
> submission guidelines.
>
To to add here that I'd love to see the coding guidelines relaxed to allow
"//" style comments!
/Bruce
Following conversation in
http://dpdk.org/ml/archives/dev/2015-September/023230.html :
On 17/12/2014 13:31, rolette at infiniteio.com (Jay Rolette) wrote:
> Signed-off-by: Jay Rolette <rolette at infiniteio.com>
> ---
Update commit title/description, maybe something like:
eal/linux: use qsort for sorting hugepages
Replace O(n^2) sort in sort_by_physaddr() with qsort() from standard
library
> lib/librte_eal/linuxapp/eal/eal_memory.c | 59 +++++++++++---------------------
> 1 file changed, 20 insertions(+), 39 deletions(-)
>
> diff --git a/lib/librte_eal/linuxapp/eal/eal_memory.c b/lib/librte_eal/linuxapp/eal/eal_memory.c
> index bae2507..3656515 100644
> --- a/lib/librte_eal/linuxapp/eal/eal_memory.c
> +++ b/lib/librte_eal/linuxapp/eal/eal_memory.c
> @@ -670,6 +670,25 @@ error:
> return -1;
> }
>
> +static int
> +cmp_physaddr(const void *a, const void *b)
> +{
> +#ifndef RTE_ARCH_PPC_64
> + const struct hugepage_file *p1 = (const struct hugepage_file *)a;
> + const struct hugepage_file *p2 = (const struct hugepage_file *)b;
> +#else
> + // PowerPC needs memory sorted in reverse order from x86
> + const struct hugepage_file *p1 = (const struct hugepage_file *)b;
> + const struct hugepage_file *p2 = (const struct hugepage_file *)a;
> +#endif
> + if (p1->physaddr < p2->physaddr)
> + return -1;
> + else if (p1->physaddr > p2->physaddr)
> + return 1;
> + else
> + return 0;
> +}
> +
There were a couple of comments from Thomas about the comments style and
#ifdef:
- Comment style should be modified as per
http://dpdk.org/doc/guides/contributing/coding_style.html#c-comment-style
- Regarding the #ifdef, I agree with Jay that it is the current approach
in the file.
> /*
> * Sort the hugepg_tbl by physical address (lower addresses first on x86,
> * higher address first on powerpc). We use a slow algorithm, but we won't
> @@ -678,45 +697,7 @@ error:
> static int
> sort_by_physaddr(struct hugepage_file *hugepg_tbl, struct hugepage_info *hpi)
> {
> - unsigned i, j;
> - int compare_idx;
> - uint64_t compare_addr;
> - struct hugepage_file tmp;
> -
> - for (i = 0; i < hpi->num_pages[0]; i++) {
> - compare_addr = 0;
> - compare_idx = -1;
> -
> - /*
> - * browse all entries starting at 'i', and find the
> - * entry with the smallest addr
> - */
> - for (j=i; j< hpi->num_pages[0]; j++) {
> -
> - if (compare_addr == 0 ||
> -#ifdef RTE_ARCH_PPC_64
> - hugepg_tbl[j].physaddr > compare_addr) {
> -#else
> - hugepg_tbl[j].physaddr < compare_addr) {
> -#endif
> - compare_addr = hugepg_tbl[j].physaddr;
> - compare_idx = j;
> - }
> - }
> -
> - /* should not happen */
> - if (compare_idx == -1) {
> - RTE_LOG(ERR, EAL, "%s(): error in physaddr sorting\n", __func__);
> - return -1;
> - }
> -
> - /* swap the 2 entries in the table */
> - memcpy(&tmp, &hugepg_tbl[compare_idx],
> - sizeof(struct hugepage_file));
> - memcpy(&hugepg_tbl[compare_idx], &hugepg_tbl[i],
> - sizeof(struct hugepage_file));
> - memcpy(&hugepg_tbl[i], &tmp, sizeof(struct hugepage_file));
> - }
> + qsort(hugepg_tbl, hpi->num_pages[0], sizeof(struct hugepage_file), cmp_physaddr);
> return 0;
> }
Why not just remove sort_by_physaddr() and call qsort() directly?
Sergio
Thanks for the feedback, Sergio. Responses inline below, but unfortunately
I don't have time to submit a new patch right now. I'm at the tail-end of
our release cycle. Last year when I originally submitted the patch, it
would have been easy to update it and resubmit.
Jay
On Wed, Sep 9, 2015 at 5:35 AM, Gonzalez Monroy, Sergio <
sergio.gonzalez.monroy@intel.com> wrote:
> Following conversation in
> http://dpdk.org/ml/archives/dev/2015-September/023230.html :
>
> On 17/12/2014 13:31, rolette at infiniteio.com (Jay Rolette) wrote:
>
>> Signed-off-by: Jay Rolette <rolette at infiniteio.com>
>> ---
>>
> Update commit title/description, maybe something like:
> eal/linux: use qsort for sorting hugepages
> Replace O(n^2) sort in sort_by_physaddr() with qsort() from standard
> library
Ok. Pretty minor, but easy enough.
> lib/librte_eal/linuxapp/eal/eal_memory.c | 59
>> +++++++++++---------------------
>> 1 file changed, 20 insertions(+), 39 deletions(-)
>>
>> diff --git a/lib/librte_eal/linuxapp/eal/eal_memory.c
>> b/lib/librte_eal/linuxapp/eal/eal_memory.c
>> index bae2507..3656515 100644
>> --- a/lib/librte_eal/linuxapp/eal/eal_memory.c
>> +++ b/lib/librte_eal/linuxapp/eal/eal_memory.c
>> @@ -670,6 +670,25 @@ error:
>> return -1;
>> }
>> +static int
>> +cmp_physaddr(const void *a, const void *b)
>> +{
>> +#ifndef RTE_ARCH_PPC_64
>> + const struct hugepage_file *p1 = (const struct hugepage_file *)a;
>> + const struct hugepage_file *p2 = (const struct hugepage_file *)b;
>> +#else
>> + // PowerPC needs memory sorted in reverse order from x86
>> + const struct hugepage_file *p1 = (const struct hugepage_file *)b;
>> + const struct hugepage_file *p2 = (const struct hugepage_file *)a;
>> +#endif
>> + if (p1->physaddr < p2->physaddr)
>> + return -1;
>> + else if (p1->physaddr > p2->physaddr)
>> + return 1;
>> + else
>> + return 0;
>> +}
>> +
>>
> There were a couple of comments from Thomas about the comments style and
> #ifdef:
> - Comment style should be modified as per
> http://dpdk.org/doc/guides/contributing/coding_style.html#c-comment-style
Yep, although that came along well after I submitted the patch
- Regarding the #ifdef, I agree with Jay that it is the current approach in
> the file.
>
> /*
>> * Sort the hugepg_tbl by physical address (lower addresses first on
>> x86,
>> * higher address first on powerpc). We use a slow algorithm, but we
>> won't
>> @@ -678,45 +697,7 @@ error:
>> static int
>> sort_by_physaddr(struct hugepage_file *hugepg_tbl, struct hugepage_info
>> *hpi)
>> {
>> - unsigned i, j;
>> - int compare_idx;
>> - uint64_t compare_addr;
>> - struct hugepage_file tmp;
>> -
>> - for (i = 0; i < hpi->num_pages[0]; i++) {
>> - compare_addr = 0;
>> - compare_idx = -1;
>> -
>> - /*
>> - * browse all entries starting at 'i', and find the
>> - * entry with the smallest addr
>> - */
>> - for (j=i; j< hpi->num_pages[0]; j++) {
>> -
>> - if (compare_addr == 0 ||
>> -#ifdef RTE_ARCH_PPC_64
>> - hugepg_tbl[j].physaddr > compare_addr) {
>> -#else
>> - hugepg_tbl[j].physaddr < compare_addr) {
>> -#endif
>> - compare_addr = hugepg_tbl[j].physaddr;
>> - compare_idx = j;
>> - }
>> - }
>> -
>> - /* should not happen */
>> - if (compare_idx == -1) {
>> - RTE_LOG(ERR, EAL, "%s(): error in physaddr
>> sorting\n", __func__);
>> - return -1;
>> - }
>> -
>> - /* swap the 2 entries in the table */
>> - memcpy(&tmp, &hugepg_tbl[compare_idx],
>> - sizeof(struct hugepage_file));
>> - memcpy(&hugepg_tbl[compare_idx], &hugepg_tbl[i],
>> - sizeof(struct hugepage_file));
>> - memcpy(&hugepg_tbl[i], &tmp, sizeof(struct
>> hugepage_file));
>> - }
>> + qsort(hugepg_tbl, hpi->num_pages[0], sizeof(struct
>> hugepage_file), cmp_physaddr);
>> return 0;
>> }
>>
> Why not just remove sort_by_physaddr() and call qsort() directly?
That would be fine. I hadn't bothered to check whether sort_by_physaddr()
was called anywhere else, so left it there. It's not, so no real value to
keeping it in this case.
>
> Sergio
>
@@ -670,6 +670,25 @@ error:
return -1;
}
+static int
+cmp_physaddr(const void *a, const void *b)
+{
+#ifndef RTE_ARCH_PPC_64
+ const struct hugepage_file *p1 = (const struct hugepage_file *)a;
+ const struct hugepage_file *p2 = (const struct hugepage_file *)b;
+#else
+ // PowerPC needs memory sorted in reverse order from x86
+ const struct hugepage_file *p1 = (const struct hugepage_file *)b;
+ const struct hugepage_file *p2 = (const struct hugepage_file *)a;
+#endif
+ if (p1->physaddr < p2->physaddr)
+ return -1;
+ else if (p1->physaddr > p2->physaddr)
+ return 1;
+ else
+ return 0;
+}
+
/*
* Sort the hugepg_tbl by physical address (lower addresses first on x86,
* higher address first on powerpc). We use a slow algorithm, but we won't
@@ -678,45 +697,7 @@ error:
static int
sort_by_physaddr(struct hugepage_file *hugepg_tbl, struct hugepage_info *hpi)
{
- unsigned i, j;
- int compare_idx;
- uint64_t compare_addr;
- struct hugepage_file tmp;
-
- for (i = 0; i < hpi->num_pages[0]; i++) {
- compare_addr = 0;
- compare_idx = -1;
-
- /*
- * browse all entries starting at 'i', and find the
- * entry with the smallest addr
- */
- for (j=i; j< hpi->num_pages[0]; j++) {
-
- if (compare_addr == 0 ||
-#ifdef RTE_ARCH_PPC_64
- hugepg_tbl[j].physaddr > compare_addr) {
-#else
- hugepg_tbl[j].physaddr < compare_addr) {
-#endif
- compare_addr = hugepg_tbl[j].physaddr;
- compare_idx = j;
- }
- }
-
- /* should not happen */
- if (compare_idx == -1) {
- RTE_LOG(ERR, EAL, "%s(): error in physaddr sorting\n", __func__);
- return -1;
- }
-
- /* swap the 2 entries in the table */
- memcpy(&tmp, &hugepg_tbl[compare_idx],
- sizeof(struct hugepage_file));
- memcpy(&hugepg_tbl[compare_idx], &hugepg_tbl[i],
- sizeof(struct hugepage_file));
- memcpy(&hugepg_tbl[i], &tmp, sizeof(struct hugepage_file));
- }
+ qsort(hugepg_tbl, hpi->num_pages[0], sizeof(struct hugepage_file), cmp_physaddr);
return 0;
}