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| author | Richard Scheffenegger <rscheff@FreeBSD.org> | 2021-03-28 21:12:03 +0000 |
|---|---|---|
| committer | Richard Scheffenegger <rscheff@FreeBSD.org> | 2021-04-16 20:51:57 +0000 |
| commit | 54beb1ef2c831394ef908ef52bac690a4fe362e0 (patch) | |
| tree | 4c40ee719d7321d40a7dd11b73eb76cc48f2a08b | |
| parent | 424f6363927a113fe5a1dcb4691039ec25cf3680 (diff) | |
| download | src-54beb1ef2c831394ef908ef52bac690a4fe362e0.tar.gz src-54beb1ef2c831394ef908ef52bac690a4fe362e0.zip | |
tcp: reduce memory footprint when listing tcp hostcache
In tcp_hostcache_list, the sbuf used would need a large (~2MB)
blocking allocation of memory (M_WAITOK), when listing a
full hostcache. This may stall the requestor for an indeterminate
time.
A further optimization is to return the expected userspace
buffersize right away, rather than preparing the output of
each current entry of the hostcase, provided by: @tuexen.
This makes use of the ready-made functions of sbuf to work
with sysctl, and repeatedly drain the much smaller buffer.
PR: 254333
MFC after: 2 weeks
Reviewed By: #transport, tuexen
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D29471
(cherry picked from commit cb0dd7e122b8936ad61a141e65ef8ef874bfebe5)
| -rw-r--r-- | sys/netinet/tcp_hostcache.c | 21 |
1 files changed, 15 insertions, 6 deletions
diff --git a/sys/netinet/tcp_hostcache.c b/sys/netinet/tcp_hostcache.c index 2753d511c9d5..6dfe3941c9d8 100644 --- a/sys/netinet/tcp_hostcache.c +++ b/sys/netinet/tcp_hostcache.c @@ -625,7 +625,7 @@ sysctl_tcp_hc_list(SYSCTL_HANDLER_ARGS) { const int linesize = 128; struct sbuf sb; - int i, error; + int i, error, len; struct hc_metrics *hc_entry; char ip4buf[INET_ADDRSTRLEN]; #ifdef INET6 @@ -635,11 +635,22 @@ sysctl_tcp_hc_list(SYSCTL_HANDLER_ARGS) if (jailed_without_vnet(curthread->td_ucred) != 0) return (EPERM); - sbuf_new(&sb, NULL, linesize * (V_tcp_hostcache.cache_count + 1), - SBUF_INCLUDENUL); + /* Optimize Buffer length query by sbin/sysctl */ + if (req->oldptr == NULL) { + len = (V_tcp_hostcache.cache_count + 1) * linesize; + return (SYSCTL_OUT(req, NULL, len)); + } + + error = sysctl_wire_old_buffer(req, 0); + if (error != 0) { + return(error); + } + + /* Use a buffer for 16 lines */ + sbuf_new_for_sysctl(&sb, NULL, 16 * linesize, req); sbuf_printf(&sb, - "\nIP address MTU SSTRESH RTT RTTVAR " + "\nIP address MTU SSTRESH RTT RTTVAR " " CWND SENDPIPE RECVPIPE HITS UPD EXP\n"); #define msec(u) (((u) + 500) / 1000) @@ -674,8 +685,6 @@ sysctl_tcp_hc_list(SYSCTL_HANDLER_ARGS) } #undef msec error = sbuf_finish(&sb); - if (error == 0) - error = SYSCTL_OUT(req, sbuf_data(&sb), sbuf_len(&sb)); sbuf_delete(&sb); return(error); } |