mempool: fix slow allocation of large mempools
Checks
Commit Message
When allocating a mempool which is larger than the largest
available area, it can take a lot of time:
a- the mempool calculate the required memory size, and tries
to allocate it, it fails
b- then it tries to allocate the largest available area (this
does not request new huge pages)
c- add this zone to the mempool, this triggers the allocation
of a mem hdr, which request a new huge page
d- back to a- until mempool is populated or until there is no
more memory
This can take a lot of time to finally fail (several minutes): in step
a- it takes all available hugepages on the system, then release them
after it fails.
The problem appeared with commit eba11e364614 ("mempool: reduce wasted
space on populate"), because smaller chunks are now allowed. Previously,
it had to be at least one page size, which is not the case in step b-.
To fix this, implement our own way to allocate the largest available
area instead of using the feature from memzone: if an allocation fails,
try to divide the size by 2 and retry. When the requested size falls
below min_chunk_size, stop and return an error.
Fixes: eba11e364614 ("mempool: reduce wasted space on populate")
Cc: stable@dpdk.org
Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
---
lib/librte_mempool/rte_mempool.c | 29 ++++++++++++-----------------
1 file changed, 12 insertions(+), 17 deletions(-)
Comments
On 09-Jan-20 1:27 PM, Olivier Matz wrote:
> When allocating a mempool which is larger than the largest
> available area, it can take a lot of time:
>
> a- the mempool calculate the required memory size, and tries
> to allocate it, it fails
> b- then it tries to allocate the largest available area (this
> does not request new huge pages)
> c- add this zone to the mempool, this triggers the allocation
> of a mem hdr, which request a new huge page
> d- back to a- until mempool is populated or until there is no
> more memory
>
> This can take a lot of time to finally fail (several minutes): in step
> a- it takes all available hugepages on the system, then release them
> after it fails.
>
> The problem appeared with commit eba11e364614 ("mempool: reduce wasted
> space on populate"), because smaller chunks are now allowed. Previously,
> it had to be at least one page size, which is not the case in step b-.
>
> To fix this, implement our own way to allocate the largest available
> area instead of using the feature from memzone: if an allocation fails,
> try to divide the size by 2 and retry. When the requested size falls
> below min_chunk_size, stop and return an error.
>
> Fixes: eba11e364614 ("mempool: reduce wasted space on populate")
> Cc: stable@dpdk.org
>
> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> ---
I don't particularly like the idea of working around this issue as
opposed to fixing it memzone-side, but since there's currently no plan
to address this in memzone allocator, this should work much better than
before.
Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>
Hi Olivier,
> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Olivier Matz
> Sent: Thursday, January 9, 2020 3:28 PM
> To: dev@dpdk.org
> Cc: Andrew Rybchenko <arybchenko@solarflare.com>; Anatoly Burakov
> <anatoly.burakov@intel.com>; stable@dpdk.org
> Subject: [dpdk-dev] [PATCH] mempool: fix slow allocation of large mempools
>
> When allocating a mempool which is larger than the largest available area, it
> can take a lot of time:
>
> a- the mempool calculate the required memory size, and tries
> to allocate it, it fails
> b- then it tries to allocate the largest available area (this
> does not request new huge pages)
> c- add this zone to the mempool, this triggers the allocation
> of a mem hdr, which request a new huge page
> d- back to a- until mempool is populated or until there is no
> more memory
>
> This can take a lot of time to finally fail (several minutes): in step
> a- it takes all available hugepages on the system, then release them after it
> fails.
>
> The problem appeared with commit eba11e364614 ("mempool: reduce
> wasted space on populate"), because smaller chunks are now allowed.
> Previously, it had to be at least one page size, which is not the case in step b-.
>
> To fix this, implement our own way to allocate the largest available area
> instead of using the feature from memzone: if an allocation fails, try to divide
> the size by 2 and retry. When the requested size falls below min_chunk_size,
> stop and return an error.
>
> Fixes: eba11e364614 ("mempool: reduce wasted space on populate")
> Cc: stable@dpdk.org
>
> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> ---
Testpmd (testpmd -n4 -- -i) fails to start after applying this patch with:
"""
EAL: Error - exiting with code: 1
Cause: Creation of mbuf pool for socket 0 failed: File exists
"""
This is why the check ci/iol-mellanox-Performance is failing (not sure if the other tests are failing for the same reason).
Regards,
Ali
Hi Ali,
On Thu, Jan 09, 2020 at 04:06:53PM +0000, Ali Alnubani wrote:
> Hi Olivier,
>
> > -----Original Message-----
> > From: dev <dev-bounces@dpdk.org> On Behalf Of Olivier Matz
> > Sent: Thursday, January 9, 2020 3:28 PM
> > To: dev@dpdk.org
> > Cc: Andrew Rybchenko <arybchenko@solarflare.com>; Anatoly Burakov
> > <anatoly.burakov@intel.com>; stable@dpdk.org
> > Subject: [dpdk-dev] [PATCH] mempool: fix slow allocation of large mempools
> >
> > When allocating a mempool which is larger than the largest available area, it
> > can take a lot of time:
> >
> > a- the mempool calculate the required memory size, and tries
> > to allocate it, it fails
> > b- then it tries to allocate the largest available area (this
> > does not request new huge pages)
> > c- add this zone to the mempool, this triggers the allocation
> > of a mem hdr, which request a new huge page
> > d- back to a- until mempool is populated or until there is no
> > more memory
> >
> > This can take a lot of time to finally fail (several minutes): in step
> > a- it takes all available hugepages on the system, then release them after it
> > fails.
> >
> > The problem appeared with commit eba11e364614 ("mempool: reduce
> > wasted space on populate"), because smaller chunks are now allowed.
> > Previously, it had to be at least one page size, which is not the case in step b-.
> >
> > To fix this, implement our own way to allocate the largest available area
> > instead of using the feature from memzone: if an allocation fails, try to divide
> > the size by 2 and retry. When the requested size falls below min_chunk_size,
> > stop and return an error.
> >
> > Fixes: eba11e364614 ("mempool: reduce wasted space on populate")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> > ---
>
> Testpmd (testpmd -n4 -- -i) fails to start after applying this patch with:
> """
> EAL: Error - exiting with code: 1
> Cause: Creation of mbuf pool for socket 0 failed: File exists
> """
>
> This is why the check ci/iol-mellanox-Performance is failing (not sure if the other tests are failing for the same reason).
Thanks for the report.
I should have retested after my "little rework"... :)
I'll send a v2 with this fix:
--- a/lib/librte_mempool/rte_mempool.c
+++ b/lib/librte_mempool/rte_mempool.c
@@ -572,7 +572,7 @@ rte_mempool_populate_default(struct rte_mempool *mp)
max_alloc_size = RTE_MIN(max_alloc_size,
(size_t)mem_size) / 2;
- } while (max_alloc_size >= min_chunk_size);
+ } while (mz == NULL && max_alloc_size >= min_chunk_size);
if (mz == NULL) {
ret = -rte_errno;
Olivier
On 1/9/20 4:27 PM, Olivier Matz wrote:
> When allocating a mempool which is larger than the largest
> available area, it can take a lot of time:
>
> a- the mempool calculate the required memory size, and tries
> to allocate it, it fails
> b- then it tries to allocate the largest available area (this
> does not request new huge pages)
> c- add this zone to the mempool, this triggers the allocation
> of a mem hdr, which request a new huge page
> d- back to a- until mempool is populated or until there is no
> more memory
>
> This can take a lot of time to finally fail (several minutes): in step
> a- it takes all available hugepages on the system, then release them
> after it fails.
>
> The problem appeared with commit eba11e364614 ("mempool: reduce wasted
> space on populate"), because smaller chunks are now allowed. Previously,
> it had to be at least one page size, which is not the case in step b-.
>
> To fix this, implement our own way to allocate the largest available
> area instead of using the feature from memzone: if an allocation fails,
> try to divide the size by 2 and retry. When the requested size falls
> below min_chunk_size, stop and return an error.
>
> Fixes: eba11e364614 ("mempool: reduce wasted space on populate")
> Cc: stable@dpdk.org
>
> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
LGTM except already mentioned bug with missing mz == NULL to retry loop.
Plus one minor question below.
> ---
> lib/librte_mempool/rte_mempool.c | 29 ++++++++++++-----------------
> 1 file changed, 12 insertions(+), 17 deletions(-)
>
> diff --git a/lib/librte_mempool/rte_mempool.c b/lib/librte_mempool/rte_mempool.c
> index bda361ce6..03c8d984c 100644
> --- a/lib/librte_mempool/rte_mempool.c
> +++ b/lib/librte_mempool/rte_mempool.c
> @@ -481,6 +481,7 @@ rte_mempool_populate_default(struct rte_mempool *mp)
> unsigned mz_id, n;
> int ret;
> bool need_iova_contig_obj;
> + size_t max_alloc_size = SIZE_MAX;
>
> ret = mempool_ops_alloc_once(mp);
> if (ret != 0)
> @@ -560,30 +561,24 @@ rte_mempool_populate_default(struct rte_mempool *mp)
> if (min_chunk_size == (size_t)mem_size)
> mz_flags |= RTE_MEMZONE_IOVA_CONTIG;
>
> - mz = rte_memzone_reserve_aligned(mz_name, mem_size,
> + /* Allocate a memzone, retrying with a smaller area on ENOMEM */
> + do {
> + mz = rte_memzone_reserve_aligned(mz_name,
> + RTE_MIN((size_t)mem_size, max_alloc_size),
> mp->socket_id, mz_flags, align);
>
> - /* don't try reserving with 0 size if we were asked to reserve
> - * IOVA-contiguous memory.
> - */
> - if (min_chunk_size < (size_t)mem_size && mz == NULL) {
> - /* not enough memory, retry with the biggest zone we
> - * have
> - */
> - mz = rte_memzone_reserve_aligned(mz_name, 0,
> - mp->socket_id, mz_flags, align);
> - }
> + if (mz == NULL && rte_errno != ENOMEM)
> + break;
> +
> + max_alloc_size = RTE_MIN(max_alloc_size,
> + (size_t)mem_size) / 2;
Does it make sense to make max_alloc_size multiple of
min_chunk_size here? I think it could help to waste less
memory space.
> + } while (max_alloc_size >= min_chunk_size);
> +
> if (mz == NULL) {
> ret = -rte_errno;
> goto fail;
> }
>
> - if (mz->len < min_chunk_size) {
> - rte_memzone_free(mz);
> - ret = -ENOMEM;
> - goto fail;
> - }
> -
> if (need_iova_contig_obj)
> iova = mz->iova;
> else
>
Hi,
On Fri, Jan 10, 2020 at 12:53:24PM +0300, Andrew Rybchenko wrote:
> On 1/9/20 4:27 PM, Olivier Matz wrote:
> > When allocating a mempool which is larger than the largest
> > available area, it can take a lot of time:
> >
> > a- the mempool calculate the required memory size, and tries
> > to allocate it, it fails
> > b- then it tries to allocate the largest available area (this
> > does not request new huge pages)
> > c- add this zone to the mempool, this triggers the allocation
> > of a mem hdr, which request a new huge page
> > d- back to a- until mempool is populated or until there is no
> > more memory
> >
> > This can take a lot of time to finally fail (several minutes): in step
> > a- it takes all available hugepages on the system, then release them
> > after it fails.
> >
> > The problem appeared with commit eba11e364614 ("mempool: reduce wasted
> > space on populate"), because smaller chunks are now allowed. Previously,
> > it had to be at least one page size, which is not the case in step b-.
> >
> > To fix this, implement our own way to allocate the largest available
> > area instead of using the feature from memzone: if an allocation fails,
> > try to divide the size by 2 and retry. When the requested size falls
> > below min_chunk_size, stop and return an error.
> >
> > Fixes: eba11e364614 ("mempool: reduce wasted space on populate")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
>
> LGTM except already mentioned bug with missing mz == NULL to retry loop.
> Plus one minor question below.
>
> > ---
> > lib/librte_mempool/rte_mempool.c | 29 ++++++++++++-----------------
> > 1 file changed, 12 insertions(+), 17 deletions(-)
> >
> > diff --git a/lib/librte_mempool/rte_mempool.c b/lib/librte_mempool/rte_mempool.c
> > index bda361ce6..03c8d984c 100644
> > --- a/lib/librte_mempool/rte_mempool.c
> > +++ b/lib/librte_mempool/rte_mempool.c
> > @@ -481,6 +481,7 @@ rte_mempool_populate_default(struct rte_mempool *mp)
> > unsigned mz_id, n;
> > int ret;
> > bool need_iova_contig_obj;
> > + size_t max_alloc_size = SIZE_MAX;
> >
> > ret = mempool_ops_alloc_once(mp);
> > if (ret != 0)
> > @@ -560,30 +561,24 @@ rte_mempool_populate_default(struct rte_mempool *mp)
> > if (min_chunk_size == (size_t)mem_size)
> > mz_flags |= RTE_MEMZONE_IOVA_CONTIG;
> >
> > - mz = rte_memzone_reserve_aligned(mz_name, mem_size,
> > + /* Allocate a memzone, retrying with a smaller area on ENOMEM */
> > + do {
> > + mz = rte_memzone_reserve_aligned(mz_name,
> > + RTE_MIN((size_t)mem_size, max_alloc_size),
> > mp->socket_id, mz_flags, align);
> >
> > - /* don't try reserving with 0 size if we were asked to reserve
> > - * IOVA-contiguous memory.
> > - */
> > - if (min_chunk_size < (size_t)mem_size && mz == NULL) {
> > - /* not enough memory, retry with the biggest zone we
> > - * have
> > - */
> > - mz = rte_memzone_reserve_aligned(mz_name, 0,
> > - mp->socket_id, mz_flags, align);
> > - }
> > + if (mz == NULL && rte_errno != ENOMEM)
> > + break;
> > +
> > + max_alloc_size = RTE_MIN(max_alloc_size,
> > + (size_t)mem_size) / 2;
>
> Does it make sense to make max_alloc_size multiple of
> min_chunk_size here? I think it could help to waste less
> memory space.
I don't think it's worth doing it: I agree it could avoid to waste
space, but it is only significant if max_alloc_size is in the same order
of size than min_chunk_size. And this would only happen when we are
running out of memory.
Also, as populate_virt() will skip page boundaries, keeping
a multiple of min_chunk_size may not make sense in that case.
>
> > + } while (max_alloc_size >= min_chunk_size);
> > +
> > if (mz == NULL) {
> > ret = -rte_errno;
> > goto fail;
> > }
> >
> > - if (mz->len < min_chunk_size) {
> > - rte_memzone_free(mz);
> > - ret = -ENOMEM;
> > - goto fail;
> > - }
> > -
> > if (need_iova_contig_obj)
> > iova = mz->iova;
> > else
> >
>
@@ -481,6 +481,7 @@ rte_mempool_populate_default(struct rte_mempool *mp)
unsigned mz_id, n;
int ret;
bool need_iova_contig_obj;
+ size_t max_alloc_size = SIZE_MAX;
ret = mempool_ops_alloc_once(mp);
if (ret != 0)
@@ -560,30 +561,24 @@ rte_mempool_populate_default(struct rte_mempool *mp)
if (min_chunk_size == (size_t)mem_size)
mz_flags |= RTE_MEMZONE_IOVA_CONTIG;
- mz = rte_memzone_reserve_aligned(mz_name, mem_size,
+ /* Allocate a memzone, retrying with a smaller area on ENOMEM */
+ do {
+ mz = rte_memzone_reserve_aligned(mz_name,
+ RTE_MIN((size_t)mem_size, max_alloc_size),
mp->socket_id, mz_flags, align);
- /* don't try reserving with 0 size if we were asked to reserve
- * IOVA-contiguous memory.
- */
- if (min_chunk_size < (size_t)mem_size && mz == NULL) {
- /* not enough memory, retry with the biggest zone we
- * have
- */
- mz = rte_memzone_reserve_aligned(mz_name, 0,
- mp->socket_id, mz_flags, align);
- }
+ if (mz == NULL && rte_errno != ENOMEM)
+ break;
+
+ max_alloc_size = RTE_MIN(max_alloc_size,
+ (size_t)mem_size) / 2;
+ } while (max_alloc_size >= min_chunk_size);
+
if (mz == NULL) {
ret = -rte_errno;
goto fail;
}
- if (mz->len < min_chunk_size) {
- rte_memzone_free(mz);
- ret = -ENOMEM;
- goto fail;
- }
-
if (need_iova_contig_obj)
iova = mz->iova;
else