[dpdk-dev] [PATCH] Revert "mem: allocate in reverse to reduce fragmentation"

[dpdk-dev] [PATCH] Revert "mem: allocate in reverse to reduce fragmentation"

[Anatoly Burakov]

This reverts commit 179f916e88e4a0fdd5ad4d20e226771d3d271c41.

A few regressions with virtio/vhost have been discovered, due to the
strong dependency of virtio/vhost on the underlying memory layout.
Specifically, virtio/vhost share all memory pages starting from the
beginning of the segment, while the patch above made it so that the
memory is always allocated from the top of VA space, not from the
bottom.

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
---
 lib/librte_eal/linuxapp/eal/eal_memalloc.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/lib/librte_eal/linuxapp/eal/eal_memalloc.c b/lib/librte_eal/linuxapp/eal/eal_memalloc.c
index a59f229cd..aa95551a8 100644
--- a/lib/librte_eal/linuxapp/eal/eal_memalloc.c
+++ b/lib/librte_eal/linuxapp/eal/eal_memalloc.c
@@ -731,8 +731,7 @@ alloc_seg_walk(const struct rte_memseg_list *msl, void *arg)
 	need = wa->n_segs;
 
 	/* try finding space in memseg list */
-	cur_idx = rte_fbarray_find_prev_n_free(&cur_msl->memseg_arr,
-			cur_msl->memseg_arr.len - 1, need);
+	cur_idx = rte_fbarray_find_next_n_free(&cur_msl->memseg_arr, 0, need);
 	if (cur_idx < 0)
 		return 0;
 	start_idx = cur_idx;
-- 
2.17.1

Re: [dpdk-dev] [PATCH] Revert "mem: allocate in reverse to reduce fragmentation"

[Thomas Monjalon]

24/07/2018 14:21, Anatoly Burakov:
> This reverts commit 179f916e88e4a0fdd5ad4d20e226771d3d271c41.
> 
> A few regressions with virtio/vhost have been discovered, due to the
> strong dependency of virtio/vhost on the underlying memory layout.
> Specifically, virtio/vhost share all memory pages starting from the
> beginning of the segment, while the patch above made it so that the
> memory is always allocated from the top of VA space, not from the
> bottom.
> 
> Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>

Applied with this fun title:
	mem: revert reversed allocation

Re: [dpdk-dev] [PATCH] Revert "mem: allocate in reverse to reduce fragmentation"

[Burakov, Anatoly]

On 26-Jul-18 10:18 AM, Thomas Monjalon wrote:
> 24/07/2018 14:21, Anatoly Burakov:
>> This reverts commit 179f916e88e4a0fdd5ad4d20e226771d3d271c41.
>>
>> A few regressions with virtio/vhost have been discovered, due to the
>> strong dependency of virtio/vhost on the underlying memory layout.
>> Specifically, virtio/vhost share all memory pages starting from the
>> beginning of the segment, while the patch above made it so that the
>> memory is always allocated from the top of VA space, not from the
>> bottom.
>>
>> Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
> 
> Applied with this fun title:
> 	mem: revert reversed allocation
> 

Next time i'll submit a patch which will revert reverted reverse 
allocation :)

-- 
Thanks,
Anatoly