On 26 Apr 2018, Rick Macklem wrote:
Ryan Stone wrote:
On Tue, Apr 24, 2018 at 4:55 AM, Konstantin Belousov
>><kostik...@gmail.com>wrote:
+#ifndef MLX5E_MAX_RX_BYTES
+#define MLX5E_MAX_RX_BYTES MCLBYTES
+#endif
Why do you use a 2KB buffer rather than a PAGE_SIZE'd buffer?
MJUMPAGESIZE should offer significantly better performance for jumbo
frames without increasing the risk of memory fragmentation.
Actually, when I was playing with using jumbo mbuf clusters for NFS, I
was able
to get it to fragment to the point where allocations failed when mixing
2K and
4K mbuf clusters.
Admittedly I was using a 256Mbyte i386 and it wasn't easily reproduced, but
it was possible.
--> Using a mix of 2K and 4K mbuf clusters can result in fragmentation,
although
I suspect that it isn't nearly as serious as what can happen when using 9K
mbuf clusters.
I used to face the fragmentation issue easily with MTU set to 9000
(x86_64 / 64GB / Connect-X/3).
I then decreased the MTU until 9K mbufs are not more used, to 4072 bytes
then.
The other used interface of this 2-ports card is set with a 1500 MTU.
Until now (about a year later), no more issue.
# vmstat -z | grep mbuf
ITEM SIZE LIMIT USED FREE REQ FAIL SLEEP
mbuf_packet: 256, 26080155, 16400, 9652, 999757417, 0, 0
mbuf: 256, 26080155, 16419, 11349, 85322301444, 0, 0
mbuf_cluster: 2048, 4075022, 26052, 550, 1059817, 0, 0
mbuf_jumbo_page: 4096, 2037511, 16400, 9522, 45863599682, 0, 0
mbuf_jumbo_9k: 9216, 603707, 0, 0, 0, 0, 0
mbuf_jumbo_16k: 16384, 339585, 0, 0, 0, 0, 0
Here's my experience :)
Ben
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