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Rewrote the space check algorithm in sbreserve() so that the extremely

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expensive (!) 64bit multiply, divide, and comparison aren't necessary
(this came in originally from rev 1.19 to fix an overflow with large
sb_max or MCLBYTES).
The 64bit math in this function was measured in some kernel profiles as
being as much as 5-8% of the total overhead of the TCP/IP stack and
is eliminated with this commit. There is a harmless rounding error (of
about .4% with the standard values) introduced with this change,
however this is in the conservative direction (downward toward a
slightly smaller maximum socket buffer size).

MFC after:	3 days
This commit is contained in:
David Greenman 2002-08-16 05:08:46 +00:00
parent 19c99159d4
commit 8c71ce8a4e
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=101966
2 changed files with 2 additions and 2 deletions
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2
sys/kern/uipc_sockbuf.c
View File

@ -392,7 +392,7 @@ sbreserve(sb, cc, so, td)
* td will only be NULL when we're in an interrupt
* (e.g. in tcp_input())
*/
if ((u_quad_t)cc > (u_quad_t)sb_max * MCLBYTES / (MSIZE + MCLBYTES))
if (cc > sb_max / (MSIZE + MCLBYTES) * MCLBYTES)
return (0);
if (!chgsbsize(so->so_cred->cr_uidinfo, &sb->sb_hiwat, cc,
td ? td->td_proc->p_rlimit[RLIMIT_SBSIZE].rlim_cur : RLIM_INFINITY)) {

2
sys/kern/uipc_socket2.c
View File

@ -392,7 +392,7 @@ sbreserve(sb, cc, so, td)
* td will only be NULL when we're in an interrupt
* (e.g. in tcp_input())
*/
if ((u_quad_t)cc > (u_quad_t)sb_max * MCLBYTES / (MSIZE + MCLBYTES))
if (cc > sb_max / (MSIZE + MCLBYTES) * MCLBYTES)
return (0);
if (!chgsbsize(so->so_cred->cr_uidinfo, &sb->sb_hiwat, cc,
td ? td->td_proc->p_rlimit[RLIMIT_SBSIZE].rlim_cur : RLIM_INFINITY)) {