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mbuf: enable ext_pgs ("unmapped") mbufs by default

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Ext_pg mbufs allow carrying multiple pages per mbuf. This
reduces mbuf linked list traversals, especially in socket
buffers, thereby reducing cache misses and CPU use for
applications using sendfile.  Note that ext_pages use
unmapped pages, eliminating KVA mapping costs on 32-bit
platforms.

Ext_pg mbufs are also required for ktls (KERN_TLS), and having
them disabled by default is a stumbling block for those
wishing to enable ktls.

Reviewed-by:	jhb, glebius
Sponsored by:	Netfix
This commit is contained in:
Andrew Gallatin 2021-01-08 13:18:42 -05:00
parent e65e4e61f5
commit 52cd25eb1a
1 changed files with 1 additions and 1 deletions
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2
sys/kern/kern_mbuf.c
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@ -116,7 +116,7 @@ int nmbjumbop; /* limits number of page size jumbo clusters */
int nmbjumbo9; /* limits number of 9k jumbo clusters */
int nmbjumbo16; /* limits number of 16k jumbo clusters */
bool mb_use_ext_pgs; /* use M_EXTPG mbufs for sendfile & TLS */
bool mb_use_ext_pgs = true; /* use M_EXTPG mbufs for sendfile & TLS */
SYSCTL_BOOL(_kern_ipc, OID_AUTO, mb_use_ext_pgs, CTLFLAG_RWTUN,
&mb_use_ext_pgs, 0,
"Use unmapped mbufs for sendfile(2) and TLS offload");