From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: Adrien Mazarguil <adrien.mazarguil@6wind.com>,
"dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH 2/2] mempool: fix pages computation to determine number of objects
Date: Mon, 25 May 2015 18:20:03 +0000 [thread overview]
Message-ID: <2601191342CEEE43887BDE71AB97725821431892@irsmsx105.ger.corp.intel.com> (raw)
In-Reply-To: <1432571266-25840-2-git-send-email-adrien.mazarguil@6wind.com>
Hi Adrien,
> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Adrien Mazarguil
> Sent: Monday, May 25, 2015 5:28 PM
> To: dev@dpdk.org
> Subject: [dpdk-dev] [PATCH 2/2] mempool: fix pages computation to determine number of objects
>
> In rte_mempool_obj_iter(), even when a single page is required per object,
> a loop checks that the the next page is contiguous and drops the first one
> otherwise. This commit checks subsequent pages only when several are
> required per object.
>
> Also a minor fix for the amount of remaining space that prevents using the
> entire region.
>
> Fixes: 148f963fb532 ("xen: core library changes")
>
> Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
> ---
> lib/librte_mempool/rte_mempool.c | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/lib/librte_mempool/rte_mempool.c b/lib/librte_mempool/rte_mempool.c
> index d1a02a2..3c1efec 100644
> --- a/lib/librte_mempool/rte_mempool.c
> +++ b/lib/librte_mempool/rte_mempool.c
> @@ -175,12 +175,17 @@ rte_mempool_obj_iter(void *vaddr, uint32_t elt_num, size_t elt_sz, size_t align,
> pgn += j;
>
> /* do we have enough space left for the next element. */
> - if (pgn >= pg_num)
> + if (pgn > pg_num)
> break;
Hmm, that doesn't look right.
Suppose:
start==0; end==5120; pg_shift==12; pg_num == 1;
So:
pgn = 1; // (5120>>12)-(0>>12)
And we end-up accessing element that is beyond allocated memory.
>
> - for (k = j;
> + /*
> + * Compute k so that (k - j) is the number of contiguous
> + * pages starting from index j. Note that there is at least
> + * one page.
> + */
> + for (k = j + 1;
> k != pgn &&
> - paddr[k] + pg_sz == paddr[k + 1];
> + paddr[k - 1] + pg_sz == paddr[k];
> k++)
> ;
Again, suppose:
j==0; start==0; end==2048; pg_shift==12; pg_num == 2;
So:
pgn = 0;
k = 1;
and the loop goes beyond paddr[] boundaries.
The problem here, I think that you treat pgn as number of pages, while it is index of last page to be used.
As I understand, what you are trying to fix here, is a situation when end is a multiply of page size (end == N * pg_sz), right?
Then, probably something simple like that would do:
- pgn = (end >> pg_shift) - (start >> pg_shift);
+ pgn = (end - 1 >> pg_shift) - (start >> pg_shift);
+ pg_next = (end >> pg_shift) - (start >> pg_shift);
...
if (k == pgn) {
if (obj_iter != NULL)
obj_iter(obj_iter_arg, (void *)start,
(void *)end, i);
va = end;
- j = pgn;
+ j = pg_next;
i++;
} else {
...
Konstantin
>
> --
> 2.1.0
next prev parent reply other threads:[~2015-05-25 18:20 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-25 16:27 [dpdk-dev] [PATCH 1/2] mempool: fix returned value on 64 bit after counting objects Adrien Mazarguil
2015-05-25 16:27 ` [dpdk-dev] [PATCH 2/2] mempool: fix pages computation to determine number of objects Adrien Mazarguil
2015-05-25 18:20 ` Ananyev, Konstantin [this message]
2015-05-26 9:14 ` Adrien Mazarguil
2015-05-27 0:41 ` [dpdk-dev] [PATCHv2] " Konstantin Ananyev
2015-05-27 7:52 ` Adrien Mazarguil
2015-05-27 8:40 ` [dpdk-dev] [PATCHv3] " Konstantin Ananyev
2015-05-29 15:58 ` Thomas Monjalon
2015-05-27 0:43 ` [dpdk-dev] [PATCH 1/2] mempool: fix returned value on 64 bit after counting objects Ananyev, Konstantin
2015-05-29 15:57 ` Thomas Monjalon
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