On 01/17/2018 06:55 PM, santosh wrote:
On Wednesday 17 January 2018 08:33 PM, Andrew Rybchenko wrote:
On 12/14/2017 04:37 PM, Olivier MATZ wrote:
On Fri, Nov 24, 2017 at 04:06:27PM +0000, Andrew Rybchenko wrote:
From: "Artem V. Andreev" <artem.andr...@oktetlabs.ru>

Clustered allocation is required to simplify packaging objects into
buckets and search of the bucket control structure by an object.

Signed-off-by: Artem V. Andreev <artem.andr...@oktetlabs.ru>
Signed-off-by: Andrew Rybchenko <arybche...@solarflare.com>
---
   lib/librte_mempool/rte_mempool.c | 39 +++++++++++++++++++++++++++++++++++----
   lib/librte_mempool/rte_mempool.h | 23 +++++++++++++++++++++--
   test/test/test_mempool.c         |  2 +-
   3 files changed, 57 insertions(+), 7 deletions(-)

diff --git a/lib/librte_mempool/rte_mempool.c b/lib/librte_mempool/rte_mempool.c
index d50dba4..43455a3 100644
--- a/lib/librte_mempool/rte_mempool.c
+++ b/lib/librte_mempool/rte_mempool.c
@@ -239,7 +239,8 @@ rte_mempool_calc_obj_size(uint32_t elt_size, uint32_t flags,
    */
   size_t
   rte_mempool_xmem_size(uint32_t elt_num, size_t total_elt_sz, uint32_t 
pg_shift,
-              unsigned int flags)
+              unsigned int flags,
+              const struct rte_mempool_info *info)
   {
       size_t obj_per_page, pg_num, pg_sz;
       unsigned int mask;
@@ -252,6 +253,17 @@ rte_mempool_xmem_size(uint32_t elt_num, size_t 
total_elt_sz, uint32_t pg_shift,
       if (total_elt_sz == 0)
           return 0;
   +    if (flags & MEMPOOL_F_CAPA_ALLOCATE_IN_CLUSTERS) {
+        unsigned int align_shift =
+            rte_bsf32(
+                rte_align32pow2(total_elt_sz *
+                        info->cluster_size));
+        if (pg_shift < align_shift) {
+            return ((elt_num / info->cluster_size) + 2)
+                << align_shift;
+        }
+    }
+
+Cc Santosh for this

To be honnest, that was my fear when introducing
MEMPOOL_F_CAPA_BLK_ALIGNED_OBJECTS and MEMPOOL_F_CAPA_PHYS_CONTIG to see more
and more specific flags in generic code.

I feel that the hidden meaning of these flags is more "if driver == foo",
which shows that something is wrong is the current design.

We have to think about another way to do. Let me try to propose
something (to be deepen).

The standard way to create a mempool is:

    mp = create_empty(...)
    set_ops_by_name(mp, "my-driver")    // optional
    populate_default(mp)                // or populate_*()
    obj_iter(mp, callback, arg)         // optional, to init objects
    // and optional local func to init mempool priv

First, we can consider deprecating some APIs like:
   - rte_mempool_xmem_create()
   - rte_mempool_xmem_size()
   - rte_mempool_xmem_usage()
   - rte_mempool_populate_iova_tab()

These functions were introduced for xen, which was recently
removed. They are complex to use, and are not used anywhere else in
DPDK.

Then, instead of having flags (quite hard to understand without knowing
the underlying driver), we can let the mempool drivers do the
populate_default() operation. For that we can add a populate_default
field in mempool ops. Same for populate_virt(), populate_anon(), and
populate_phys() which can return -ENOTSUP if this is not
implemented/implementable on a specific driver, or if flags
(NO_CACHE_ALIGN, NO_SPREAD, ...) are not supported. If the function
pointer is NULL, use the generic function.

Thanks to this, the generic code would remain understandable and won't
have to care about how memory should be allocated for a specific driver.

Thoughts?
Yes, I agree. This week we'll provide updated version of the RFC which
covers it including transition of the mempool/octeontx. I think it is sufficient
to introduce two new ops:
  1. To calculate memory space required to store specified number of objects
  2. To populate objects in the provided memory chunk (the op will be called
      from rte_mempool_populate_iova() which is a leaf function for all
      rte_mempool_populate_*() calls.
It will allow to avoid duplication and keep memchunks housekeeping inside
mempool library.

There is also a downside of letting mempool driver to populate, which was 
raised in other thread.
http://dpdk.org/dev/patchwork/patch/31943/

I've seen the note about code duplication. Let's discuss it when v2 is sent.
I think our approach minimizes it and allows to have only specific code in the
driver callback.

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